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Diet and Cancer Survivorship
Natalie Ledesma, MS, RD, CSO and Ernest H. Rosenbaum, MD
Diet Lifestyle History
Healthy Prudent Diet
Nutrition and Diet
Essential Fatty Acids
Body Mass, Obesity and Cancer
Diet Lifestyle History
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In the early 1900s, about 40% of the average person's diet came from fruits, vegetables and grains. Canned foods were homemade, and most people lived on farms or close enough to get farmed food, which was unprocessed - meat, fruits, vegetables, dairy products, grains, legumes, and nuts/seeds. Recently, we have noted that consumption of these products has dropped from 40% of our diets to 20%. The consumption of fats has increased. In 1910, fat consumption was 31% of calories and sugar between 12 and 18% of total calories. During 1971-2000, the percentage of calories from fat decreased from 36.9% to 32.8% for men and from 36.1% to 32.8% for women. However, total fat intake increased among women by 6.5 grams and decreased among men by 5.3 grams. 
Between 1971-1974 and 1999-2000, carbohydrate consumption increased from 42.4% to 49.0% in men and from 45.4% to 51.6% in women. Total caloric intake from beverages has increased from 236 kcals/day in 1965 to 458 kcals/day in 2002. A significant proportion of those calories were from sweetened soft drinks and alcohol. With industrialization and urbanization, consumption of whole grains decreased, as more refined cereals were developed, which are devoid of fiber and more energy-dense, containing fats, sugar, and salt. Thus, overall, a statistically significant increase in average energy intake occurred during 1971-2000. The average energy intake increased for men from 2,450 kcals to 2,618 kcals (+168 calories), and for women, from 1,542 kcals to 1,877 kcals (+335 calories).
It is believed that these unhealthy dietary changes have contributed to the increased incidence of cancer along with tobacco, alcohol, and physical inactivity. One-third of the 500,000 cancer deaths that occur annually in the U.S. can be attributed to diet and physical activity, while another third is due to tobacco exposure. The evidence that diet is a risk factor has been under study over the last forty to fifty years, especially in Western countries. Western lifestyles are often characterized by a high caloric intake, physical inactivity, a diet high in animal protein and fat, and high in rapidly digestible carbohydrates or sugars. This lifestyle has been associated with the higher rates of breast, colorectal, prostate, endometrial, and lung cancers. The diet in developing countries, on the other hand, usually consists of starchy staple foods with a low intake of animal protein and fat, and sugar and low rates of these cancers. Over the last half century, many countries have had changes in their diets, usually with increased consumption of meat, dairy products, vegetable oils, fruit juices, alcoholic beverages and a decrease in starchy, staple foods, such as bread, potatoes, rice and maize flour. There has also been a reduction in physical activity that has promoted the increase in obesity, which is an additional major risk factor for cancer.
A good example of this effect is Japan, where the consumption of meat and dairy products increased ten-fold between the 1950s and 1990s, with trends changing in cereal and meat consumption, and a reflected increase in colorectal cancer in the United Kingdom (UK) and Japan since 1960. Forty years ago, consumption of cereals was higher in Japan than in the UK; whereas, consumption of meat was high in the UK and low in Japan. Since then, cereal consumption has fallen in both countries, and consumption of meat has increased seven-fold in Japan and has remained constant in the UK. The incidence of colorectal cancer rose by 35% in men in the UK and five-fold in Japan and now is approaching the same level in both Japan and the UK. Thus, it is concluded from these studies, as well as others, that diet is an important risk factor for many of the common cancers, and it is felt that changing to a healthier, prudent-type diet, with a higher intake of fruits and vegetables, a decreased intake of meats, maintenance of a healthy body weight, and an increase in physical activity can be essential in reducing the risk of cancer.
Healthy Prudent Diet
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Sixty-five percent of Americans diagnosed with cancer now live more than five years. Nutrition and exercise are two areas in which healthy lifestyle changes can help reduce the risk of recurrent and new cancers and promote survival. Cancer survivors are at an approximately 15% increased risk for developing secondary tumors, as well as multiple comorbid problems. By implementing health-related lifestyle behavioral changes, one can improve quality of life and hopefully survival by reducing comorbidities. 5-8 The healthy prudent diet is an optimal diet for cancer, heart disease, and other comorbid diseases. By increasing the food intake of fruits, vegetables, legumes, and whole grains you can promote better health. There is a correlation between the risk of cancer and heart disease when the LDL cholesterol is elevated (due to having too much cholesterol, saturated fat and trans fats in the diet and/or a hereditary predisposition.). A recent study found that stage III colon cancer survivors had a greater risk of relapse after surgery if their diet was heavy in red meat, fat and refined grains. Additionally, the American population is progressively gaining weight; one-third of the population is overweight and another third is obese. It is estimated that obesity relates to 14% of cancer deaths in men and 20% of cancer deaths in women. By controlling what you eat and how much you exercise, you can reduce your risk and live both healthier and longer. Dieting and maintaining a healthy weight can be made easier by following the healthy prudent diet.
- The Healthy Prudent Diet
- - Eat a well balanced diet
Eat a variety of 8-10 servings of fruits and vegetables daily
Opt for vibrantly colored fruits and vegetables
Increase cruciferous vegetables, members of the cabbage family
Increase vegetables high in carotenoids, orange and dark green vegetables
- Consume a high fiber diet (30-35 g/day). Increase beans and whole grains (brown rice, oatmeal, quinoa, corn tortillas, whole grain breads and pastas).
- Avoid processed and refined grains/flours/sugars
- Aim for a low fat diet (~20% fat calories). Limit saturated fats to 8% of calories.
Decrease animal fats, trans fats, and processed meats
Increase cold-water fish (salmon, herring, black cod, mackerel, and sardines)
Include healthy fats in the diet, such as flaxseed, avocado, olive oil, and soybeans.
- Limit salt-cured, smoked and nitrate-cured foods
- Limit fried and barbecued foods
- Limit alcohol consumption
- Drink 1-4 cups of green tea daily
- Physical activity to help achieve and/or maintain a healthy body weight
Nutrition and Diet
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A diet based on plant foods, legumes, whole grains, and less red meat, a daily routine for physical activity, good sleep habits, avoidance of tobacco and toxic substances, and limited alcohol intake may decrease the risk of recurrence or a new secondary cancer, likely reduce the risk of toxic cancer treatment-related side effects, prevent comorbid diseases, and is expected to promote survival.
- Plant-Based Diet
Fruits and Vegetables
- - Fruits and vegetables are great dietary sources of vitamins, minerals, fiber, and various cancer-fighting phytonutrients. A key indicator of phytonutrient content is their vibrant, intense color. Extensive research reports that diets rich in fruits and vegetables are associated with a lower risk of many cancers.[10-14] While there is yet no current proven evidence that they do reduce the risk of cancer recurrence, there are a myriad of benefits that one gains by eating a diet rich in fruits and vegetables. Research indicates that foods themselves are likely more protective against cancer than isolated compounds in supplement form.
- Recent studies have suggested that increasing vegetable consumption can have beneficial effects on reducing recurrence or increased survival for breast, prostate and ovarian cancers . Eating five or more vegetables and fruits daily in addition to 30 minutes or more of walking six days/week decreased the risk of death after early stage breast cancer by ~50%. Higher intakes of colorful fruits and vegetables yield lower incidences of colorectal, lung, oral, esophageal and stomach cancers with a decrease in recurrence and an increased survival. There is evidence that non-starchy vegetables are probably protective against cancers of the mouth, larynx, esophagus and stomach, and allium (garlic) is also protective for this group, as well as lung and colorectal cancers. A Greek study reported that increasing vegetable intake by 230g/day (~2.75 servings) and fruit intake by 200g/day (~2.4 servings) decreased mortality by 12% and 18%, respectively. Additionally, in the Spanish cohort of the EPIC trial, a decreased mortality was associated with increased intakes of fresh fruits and vegetables, primarily root vegetables and fruiting vegetables. The reduced risk of death has been attributed to the vegetables' high vitamin C content, provitamin A carotenoids, and lycopene.
- So, how many fruits and vegetables should you eat daily? Well, the answer is not exactly clear, but it may be that a minimum of 8-10 servings of fruit and vegetables are needed to provide the greatest protection against cancer. Aim for five or more vegetable servings and three or more fruit servings daily. One serving equates to: 1/2 cup fruit or vegetable, 1 cup raw leafy greens, 1/4 cup dried fruit or vegetable, and 6 fl oz fruit or vegetable juice.
- Dietary Fiber
- - A plant based diet is naturally high in fiber. A diet rich in natural fiber obtained from fruits, vegetables, legumes, and whole grains may reduce the risk of various cancers and/or their progression. Moreover, there is considerable evidence of the preventive benefits against heart disease, stroke, type 2 diabetes, and various inflammatory diseases.
- The Role and Advantages of Whole Grains
- - The average American eats less than one serving of whole grains per day, and a mere 7% get three servings as recommended, according to a recent USDA survey. Before the Industrial Revolution, all grains were whole; from the germ, bran, and endosperm of unprocessed grains. Following the Industrial Revolution, roller milling changed the way of processing grain at the end of the 19th century, where mass production of refined grains occurred, which unfortunately changed the quality of milled grains. The nutritionally rich germ and bran were removed from whole grains during the processing, making the grains fatter and easier to cook, but of less nutritive value. Whole grains are a better source of fiber, and processed fiber is not as beneficial as whole grain fiber. Additionally, the loss of vitamins, minerals, and phytochemicals occurs with the removal of the germ and the bran in the refining process.
- Fiber and Cancer
- - Dietary fiber has been shown to offer protective effects against various cancers. Fiber intake and the consumption of cereals, nuts, and seeds has been inversely associated with prostate cancer [22-23] and prostate cancer mortality , respectively. Fiber binds to toxic compounds and carcinogens, which are then later eliminated from the body. In an NCI study of 489,611 adults, fiber from whole grains modestly reduced the risk of colorectal cancer. Women who ate beans and lentils at least twice a week had a 24% lower risk of developing breast cancer compared to women who ate them less than once a month. In pre-menopausal women, fiber from cereals was associated with a significant decrease risk of breast cancer. Furthermore, the risk of dying from breast cancer significantly decreased with a diet high in fiber.
- Various mechanisms have been proposed for the protective effects of dietary fiber against cancer. These include, a) increased fecal bulk and decreased intestinal transit time, which allow less opportunity for fecal mutagens to interact with the intestinal epithelium, b) binding to bile acids, which are thought to promote cell proliferation, c) fermentation in the gut, producing short-chain fatty acids, which improve the gut environment,[30-31] and d) the antioxidants in whole grains, which have been linked to disease prevention. Moreover, a high fiber diet decreases circulating hormone levels that may promote cancer and/or its progression.[30,32]
- Additionally, high fiber foods are low in energy density and very satiating. Thus, fiber is important for weight management. Being overweight, obese, and even weight gain have been linked to many cancers, including breast, esophageal, colorectal, pancreatic, ovarian, uterine, kidney, thyroid, gallbladder, liver, and prostate.
- Survivors may wish to aim for 30-45 grams of fiber daily: a) choose breads with three or more grams of fiber per slice, b) first ingredient on the label should be whole or sprouted grain flour, not white flour, unbleached white flour, or enriched wheat flour, c) whole grains include, among others, oats, barley, brown rice, quinoa, amaranth, bulgur, millet, buckwheat, spelt, wild rice, and teff.
- Refined Carbohydrates/Sugar
- - Refined carbohydrates and high sugar foods are generally low in nutrient value and low in dietary fiber. Evidence suggests that refined cereals (primarily breads and pasta) [33-35] and desserts [34-36] have been associated with cancer. Additionally, these foods appear to increase serum insulin and serum insulin-like growth factor (IGF-I) levels, which lead to the development and promotion of cancer. IGF-I may speed tumor development by inhibiting apoptosis (normal programmed cell death), enhancing cell growth, promoting synthesis of sex steroids such as estrogen and testosterone , and inhibiting the synthesis of sex hormone-binding globulin (SHBG). A recent study observed that in fact a diet high in refined carbohydrates did lead to high blood levels of insulin and increased tumor growth. Refined carbohydrates to be consumed in limited amounts include products made with refined flours (for example: white bread, white rice, white pasta) or refined grains, alcohol, and sweets, such as candy, cookies, cakes, and pastries.
- - Many studies have suggested an association between meat intake and cancer. There are various plausible mechanisms of why the two may be related. While the benefits of phytochemicals were noted above, animal products contain none. One of the original theories linking meat to cancer was related to fat content and the greater amount of saturated fat in meat. Additionally, animal protein increases IGF-I, a growth hormone. More recent theories have examined the relationship between genotoxins, such as heterocyclic amines (HCAs) and polycyclic aromatic hydrocarbons (PAHs), and the risk of cancer.[41-44] These carcinogenic compounds form when meat is cooked at high temperatures by dry-heat methods, including frying, grilling, broiling, and barbecuing. Another thought implicates the iron content (heme) in red meat that may generate free radicals in the colon that damage DNA . A recent trial observed that total meat and processed meat were directly related to the risk of stomach, colon, rectum, pancreas, lung, breast (mainly postmenopausal), prostate, testis, kidney, bladder, and leukemia. Red meat was significantly associated with colon, lung (mainly in men), and bladder cancer. No relation was observed for cancer of the ovary, brain, and NHL. No consistent excess risk emerged for fish and poultry, which were inversely related to the risk of a number of cancer sites.
- Dietary Fat
- - Dietary fat has been implicated as a risk factor for some cancers. Most researchers agree to aim for ~20% of total calories from fat. The use of a low fat diet is beneficial for several cancers. While the Women's Healthy and Eating Living (WHEL) Study reported no effect on fat and breast cancer recurrence, it is very possible that the fat content in the women's diets were too high. The Women's Intervention Nutrition Study (WINS) reported that a 20% fat diet decreased the risk of breast cancer recurrence by 24%. However, the type of fat may be of greater significance than the total amount of fat.
- Saturated Fat
- - Saturated fats from meat and dairy products have been associated with the risk of breast, prostate, and pancreatic cancer [49-53] and metastatic prostate cancer. Although the research is currently inconclusive, it is suggested to reduce or eliminate meats and whole milk dairy products, including cheese and ice cream. Limit use of butter and baked goods.
- Trans Fat
- - Trans fats, or hydrogenated oils, have been associated with cancer, including breast, prostate, and colon.[55-59] Additionally, they are known to be atherogenic, causing heart disease. Avoid trans fats, such as margarine, fried foods, commercial peanut butter, salad dressings and processed foods including breads, crackers, cereals, and cookies.
Essential Fatty Acids
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- Omega-6 and Omega-3 Fatty Acids
- - Current research suggests that the levels of essential fatty acids and the balance between them may play a critical role in the prevention and treatment of cancer and other chronic illnesses.[60-61] This review noted that the ratio of 2.5:1 omega-6:omega-3 fats reduced rectal cell proliferation in patients with colorectal cancer, whereas a ratio of 4:1 with the same amount of omega-3 fats had no effect. Additionally, the lower omega-6:omega-3 ratio in women with breast cancer was associated with decreased risk.
- Although not all studies have observed an association between cancer and omega-6 fatty acids (linoleic acid, which can be converted to arachidonic acid), a high intake of omega-6 fatty acids may increase tumor growth.[53, 62-63] Furthermore, studies are now linking the effect of omega-6 fatty acids in the diet to stimulating growth-related genes.[64-65] Dietary sources of omega-6 fats, specifically arachidonic acid, include meat, butter, egg yolks, whole milk, and whole milk products. Common vegetable oils, such as corn oil, safflower oil, sunflower oil, and cottonseed oil, and processed foods made with these oils are dietary sources of linoleic acid.
- On a more positive front, omega-3 fatty acids [alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexanaenoic acid (DHA)] may reduce the risk of cancer and its progression.[62-63, 66] These fats are also known to strengthen the immune system and have anti-inflammatory effects. Possible mechanisms proposed for omega-3 fats protective effects include inducing apoptosis, suppressing cancer cell initiation, competing with arachidonic acid, modifying gene expression. Dietary sources of omega-3 fats include cold-water fish (for example: salmon, sardines, black cod, trout, herring), flaxseeds, chia seeds, walnuts, hempseeds, and pumpkin seeds.
- Fish and plant-based foods, however contain different types of omega-3 fatty aicds. Fish contain EPA and DHA, two specific fatty acids that have shown the most promising anticancer effects. The plant-based omega-3's, such as those listed above, contain ALA. In an ideal environment, ALA is converted to EPA and DHA; however, this process is inefficient.[68-69] However, the conversion process is enhanced with a diet low in saturated fats and a more balanced omega-6:omega-3 fat ratio. That said, if you are considering an omega-3 fatty acid supplement, choose one that is highest in EPA and DHA concentration.
- Omega-9 Fatty Acids
- - Other fats, all derived from plant sources, that appear to be neutral[70-71] or possibly protective [72-73] for some cancers are the omega-9 fatty acids, also known as monounsaturated fats. Dietary sources include extra-virgin olive oil, canola oil, macadamia nut oil, almonds, and avocados.
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Vitamin D is a fat-soluble vitamin found primarily in fatty fish and in some fortified products, such as milk, soy milk, cereals, and orange juice. Generally, our dietary intake is not adequate to meet the normal daily requirements. More often, we generate vitamin D through skin synthesis of sunlight (ultraviolet rays). It has been shown that 15 minutes of sunlight can produce up to 10,000 IU vitamin D. However, vitamin D absorption declines with age, and vitamin D deficiency is not uncommon among older adults.[74-77] Additionally, those living in northern latitudes, those with darker skin, and those with minimum sun exposure are at greater risk of vitamin D deficiency. It has been speculated that with the fear of skin cancer, fewer people are getting adequate sunshine, which may be causing a vitamin D deficiency. 
- The benefits of vitamin D are many, including observed protective effects against cancer, bone disease, heart disease, infections, inflammatory conditions, and multiple sclerosis. Also of note is that there is less cancer in areas of greater sunshine and more cancer in the northern latitudes in both the United States and Canada, making the need for vitamin D supplements essential for many people.  A recent article reported that individuals receiving a higher dose of vitamin D via supplementation had a 60% decreased risk of cancer. A meta-analysis of 18 randomized controlled studies reported that people taking vitamin D supplements, 400-800 IU per day, had a 7% reduction in total mortality rates. 
Vitamin D levels have been linked to increased cancer survival. In a study of non-small cell lung cancer patients, it was observed that after six years of follow up, those with higher levels of vitamin D had a 36% increase in patient survival versus those with low levels of vitamin D.  This effect was more prominent in early stage and SCLC stage IB-IIB; those with the highest vitamin D levels had a 50% increase in overall survival and a 45% increase in recurrence-free survival. Women with higher blood levels of vitamin D had a 47% lower risk of colon cancer over a ten-year period, and male health workers also had a 54% lower colon cancer risk. The author suggested that the supplementation of vitamin D may be able to prevent 30-50% of colon cancer cases. Moreover, a Canadian study recently reported that only 24% of women in the study had sufficient blood levels of vitamin D when diagnosed with breast cancer. Women with deficient levels of vitamin D were nearly twice as likely to have their cancer recur or spread over the next 10 years, and 73% more likely to die of the disease.
Exactly how vitamin D works is still under investigation. There are vitamin D receptors on cells, and it has been suggested that vitamin D inside the cell nucleus helps promote gene functional on-and-off switches. This may relate to possible benefits for cancer (colon, breast, lung, prostate) as well as promote, along with calcium, increased bone density to help reverse osteopenia/osteoporosis.
Five to fifteen minutes of sun exposure two or three times weekly to face, hands, arms, and back without sunscreen generally provide sufficient vitamin D. However, in light of the recent research and the use of sunscreen, additional supplementation may be necessary. Multivitamins usually contain 400 IU, and it is now believed that the recommended dose should be between 800 and 2,000 IU per day. Research now indicates that vitamin D3 is better absorbed than vitamin D2.
Due to the likelihood of a biochemical deficiency without clinical symptoms or signs, a serum 25-hydroxy-vitamin D level is recommended. Optimal serum 25-hydroxy vitamin D levels have not been established though research suggests 36-40 ng/ml may be ideal.  Some believe the normal level of vitamin D should be 50-60 ng/ml. Elderly patients over age 60 often have levels of only 20 ng/ml or less in the winter. Thus, more exact dosing of vitamin D supplementation can be made once a serum 25-hydroxy-vitamin D level has been established.
Body Mass, Obesity and Cancer
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Being overweight is approaching epidemic proportions in the United States; 65% of the American population is overweight or obese, and excess fat affects prognosis of many diseases, including cancer, heart disease, hypertension, strokes, and diabetes.  It is estimated that medical expenses for overweight and obese individuals accounted for 9.1% of total U.S. medical expenditures in 1998 and may have reached as high as $78.5 billion ($92.6 billion in 2002 dollars). The ACS has reported that although 83% of Americans know that obesity is related to heart disease and 57% know the relationship to diabetes, only 17% know that an increase in weight increases the risk for cancer. It is estimated that 20% of all cancer-related mortality is associated with patients having an overweight or obese body mass.
Elderly men who were overweight or obese at age 65 had 6-13% more lifetime health care expenditures than the same age normal weight cohort. Elderly women who were overweight or obese at age 65 spent 11-17% more than those in a normal weight range. Both elderly men and women who were overweight or obese at age 65 had worse health outcomes than the normal weight cohorts.
An elevated body mass index (BMI) or increased waist circumference is correlated with reduced longevity. Yet even a 5-10 pound weight loss can reduce the risk of disease.
Body Mass Index (BMI)
BMI is one of the ways of estimating a healthy weight (should vary between 18.5 and 24.9). Higher and lower values are proportional to increased risk of various health conditions. A BMI between 25-30 is considered overweight and a BMI of greater than 30 is considered obese. However, BMI may not be a good measure for athletes with increased muscle mass, pregnant women, and children.
BMI = Weight (kilograms)/Height (meters)2 Or BMI = Weight (pounds)/Height (inches) 2 x 703
The waist-hip ratio, determined by taking the waist measurement and dividing it by the hip measurement, is a valid way to assess health risk. Abdominal adiposity was strongly and positively associated with all-cause, cardiovascular disease, and cancer mortality independently of body mass index . In another study, those with a waist-hip ratio of ~1 or higher were shown to be 40% more likely to die of cardiovascular disease than those with a ratio of 0.8 or lower. For the waist measurement: over 35 inches for women is high risk and moderate risk is over 31.5 inches. For men, a waist measurement of 40 inches or more is high risk and over 37 inches is moderate risk. The bottom line is watch your waistline and be as lean as possible.
Waist/Hip Ratio = Waist Size (inches) / Hip (inches)
Body Mass and Cancer
Body fatness has been linked to many cancers, including colon, rectum, pancreas, kidney, esophagus, endometrium, liver, gallbladder, postmenopausal breast cancer, and advanced prostate cancer.  Excess body weight has also recently been linked to multiple myeloma in a meta-analysis.  The increase in body fat is primarily due to physical inactivity and increased calorie intake. The AICR/WCHF report confirms that excess body weight, especially if carried around the waist, increases the risk for cancer.
Postmenopausal breast, endometrial (uterine), colon, kidney, pancreas, and aggressive prostate cancers have been studied extensively and show a direct relationship to overweight and obesity. Many other cancers are also linked with overweight and obesity including adenocarcinoma of the esophagus, gallbladder, thyroid, ovary, cervix, multiple myeloma, and non-Hodgkin's lymphoma. There is a 20% increased risk of cancer for those with a BMI greater than 30.  In large studies, it has been shown that gaining over 50 pounds during adulthood doubles the risk for breast cancer. This risk can be reduced through weight loss. Reducing weight by 22-25 pounds appears to reduce breast cancer risk in half. Recent data have consistently found that overweight and obesity are also associated with progressive prostate cancer disease and increased overall mortality.
People with elevated BMIs have a higher risk of pancreatic, gallbladder, kidney, cervical, ovarian and non-Hodgkin's lymphoma cancers. Endometrial cancer has also been linked to obesity, as the risk of development increases three to five times for women with a BMI greater than 23.5. One estimate is that 40% of endometrial cancers relate to obesity. There is an increased risk for colon cancer in those with enlarged waists and a BMI greater than 27 and for breast cancer in postmenopausal woman, especially in those who have never used postmenopausal hormone therapy. It is important to distinguish between being overweight and obese. Survivors who are slightly overweight may not have as significant of an increased risk of the above-mentioned cancers. A study in the British Medical Journal reporting both incidence and mortality found that 4% of cancers were associated with obesity and 1% with being overweight. 
According to a Reuters report, as BMI increased from normal to overweight or from overweight to obese, the risk of thyroid cancer increased by 33%, and increased 24% for colon and kidney cancers in men.  Furthermore, the risk of gall bladder cancer increased 59% and kidney cancer risk increased 34% in overweight women compared with women in the normal BMI range. Higher BMI in men raised the risk of esophageal cancer by 52% and thyroid cancer by 33%.  In women, a higher BMI increased the risk of endometrial cancer by 59% and esophageal cancer by 51 percent. Furthermore, an increase in BMI was associated with an increased risk of leukemia, lymphoma, malignant melanoma in men and postmenopausal breast and pancreatic cancers in women.
This data was further supported in a Korean study where obesity clearly increased the risk of many types of cancer and that obesity-related cancers appear to be rapidly increasing in Korea and many other Asian countries, and controlling the obesity epidemic could be an effective tool for prevention of these cancers.  Adenocarcinoma of the colon and recto- sigmoid, hepatocellular carcinoma, cholangiocarcinoma, adenocarcinoma of the prostate, renal cell carcinoma, papillary carcinoma of the thyroid, small-cell carcinoma of the lung, non-Hodgkin's lymphoma and melanoma all had a positive dose-dependent relationships with BMI.
On a positive note, a large study demonstrated that weight loss of 10 or more lbs between ages 18 and 30 decreased overall likelihood of being diagnosed with breast cancer by 34% and reduced likelihood of earlier breast cancer (diagnosed between the ages of 30 and 40) by 53%. 
Body Mass and Hormones
Body fat, especially abdominal fat, is an active metabolic tissue that can produce hormones, such as estrogens, and protein chemicals, such as cytokines, which promote inflammation that can cause heart disease and cancer. In addition, excess body fat can stimulate the production of insulin, and high insulin levels are related to many forms of cancer, including breast, prostate, and probably colon cancer. Exercise has been shown to reduce insulin levels. Insulin growth factors also influence the body's cells to increase growth rate and are important in the development of cancer. Postmenopausal obesity increases free estrogens, in part due to aromatization of androstenedione to produce estrogen and estradiol and decrease sex hormone-binding globulins. The increase in these compounds may inhibit apoptosis, the mechanism by which a cancer cell commits suicide. 
Obesity, Cancer, and Survival
Obesity is associated with increased cancer recurrence in prostate and breast cancers with subsequent reduced quality of life.  Overweight or obesity is associated with poorer prognosis in the majority of the studies that have examined body mass and breast cancer. [101-107] Obesity has been linked in both pre- and post-menopausal women for cancer recurrence and a reduced survival. In younger breast cancer patients, obesity showed a 50% increased risk of dying in a ten-year follow-up study. There is also a link to survival in those with elevated BMIs or a large waist circumference, especially for postmenopausal women, where the incidence of colorectal cancer is doubled. Of note, an increased risk of death has also been observed for underweight women. Underweight can sometimes be a sign of an occult cancer.
Obesity relates to a higher grade, more aggressive prostate cancer with increased risk of recurrence post-radical prostatectomy.  Men with prostate cancer who maintained a healthy body weight were less likely to have a recurrence.  Obese men had a 30% increased risk of cancer recurrence, compared with those with lower body weights. Very obese men (BMI>35) heightened their risk of recurrence by 69%.
Additionally, weight gain after diagnosis also increases the risk of death.  Data suggest that weight gain during adult life, specifically since menopause, increases the risk of breast cancer among postmenopausal women, whereas weight loss after menopause is associated with a decreased risk of breast cancer.
Energy Balance Energy Balance = Calorie Intake +/- Calories Expended (exercise and basal metabolic rate)
Excess intake promotes weight gain. Currently, 60-70% of the American population is either overweight or obese, in part due to excessive calorie intake and less energy expended (decreased exercise). Current trends including increasing portion size, the consumption of high-caloric convenience foods, beverages, and restaurant meals, and lower levels of physical activity are all contributing to the obesity epidemic.
Assessing Energy-Dense Foods
The same size portion of energy-dense food will have many more calories than a low energy-dense food. Energy-dense foods include highly processed foods, which often have less fiber, and increased fats and sugar, such as products made from refined grains or flours, chips, baked goods, crackers, candies, butter, oils, and salad dressings. In contrast, low energy-dense foods, such as fruits, vegetables, and legumes have more fiber and higher water content. Moderate energy-dense foods include low-fat milk, lean meats, and whole grains.
It is important to control the size of the servings that we eat in order to reduce excess calories. Instead, focus on low energy-dense foods where you can have larger portion sizes. Additionally, increase water intake and avoid sugary drinks. For example, your dinner plate may be filled with ~50% vegetables, 25% lean protein, and 25% whole grain.
The Role of Physical Activity
The primary way to boost your metabolic rate is to increase physical activity - walking, tennis, baseball, basketball, aerobic exercises (stationary bike, stair climber), biking, jogging, dancing, swimming and increasing activities of daily life, which includes housework, gardening, etc., and reducing inactivity, such as watching television. The intensity of exercise, such as using weights and more vigorous activity, helps promote burning of excess calories. Weight lifting, flexibility and balance training are also important, especially to build lean muscle mass, help maintain a healthy body, and reduce the risk of falls and accidents. Even a daily reduction of 50-100 calories with exercise can promote effective weight loss.
A prospective study suggested that men in the highest category of exercise reduced their risk of advanced prostate cancer by 36% compared to the non-exercisers. The risk of fatal prostate cancer was reduced by 33%. This research was further supported by recent evidence that vigorous physical activity was associated with a lower risk of dying from prostate cancer. Quality of life and other health-related outcomes significantly improved with the combination of aerobic and resistance exercise soon after the completion of breast cancer therapy. Eating five or more vegetables and fruits daily in addition to 30 minutes or more of walking six days/week decreased the risk of death after early stage breast cancer by ~50%.
While there are various therapeutic benefits of physical activity, research indicates that exercise training alters IGF-I to lower the risk of cancer.[115-116] Additionally, a 25-50% decrease in sex hormones, such as estrogen, progesterone, and testosterone, occurs with exercise. This hormonal change may also delay the onset of cancer. Furthermore, evidence affirms that individualized exercise programs are effective to enhance muscular function and improve the quality of life of cancer survivors.  Healthy weight control is encouraged through a healthful plant based diet and regular exercise to maintain or increase lean muscle mass.
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In summary, by controlling excess calories, modifying diet, not smoking or chewing tobacco, limiting alcohol, and increasing physical activity to help maintain or achieve a healthy body weight, can help you be healthier and also prevent many comorbid diseases. By transitioning towards a plant-based diet rich in vegetables, fruits, legumes, and whole grains, following a low, but healthy fat diet, limiting red meats and other energy-dense foods, such as sugars, you will optimize your health. Maintaining a healthy diet and lifestyle is a lifelong process. The goal is to be as lean as possible within the normal body weight range (BMI 18.5-24.9). Avoid weight gain and increased waist circumference throughout your life -- from childhood and adolescence and through adulthood. Thus, by adopting a healthy lifestyle, you can promote longevity, greater quality of life and personal satisfaction, and reduce the risk of cancer and heart disease, diabetes, hypertension, stroke, and several other related diseases.
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