Whether you are slim or obese, one thing is clear: calorie-dense processed foods increase cancer risk, regardless of body weight.

Researchers studied data from 92,000 postmenopausal women who took part in the Women’s Health Initiative, a 15-year study of health in postmenopausal women. They focused on the energy density of the women’s diets – “high energy” diets are synonymous with “high calorie” diets – and noted the number of calories per gram of the total diet.

The researchers made an unexpected finding: Women in the top fifth of energy density were 10 percent more likely to be diagnosed with an obesity-related cancer compared to the bottom fifth, and this relationship was found in women who were at a normal weight at baseline.² These cancers include colorectal, pancreatic, endometrial, ovarian, liver, kidney, gallbladder, and postmenopausal breast cancers.¹ This increase in risk was associated with the calorie density of the women’s diets.²

The results suggested: If you choose low-nutrient, energy-dense foods, it will affect your health even if it doesn’t affect your waistline. Just because you’re slim doesn’t mean junk food isn’t damaging your health.

Energy density vs. nutrient density

Dietary energy density in this study was defined as the number of calories per gram in a food of the entire diet. For the most part, typical high energy-dense foods, such as baked goods, French fries, burgers, pizza and desserts, are low in nutrient density (micronutrients per gram). High nutrient-dense foods, such as vegetables, fruits, and legumes, tend to be low in energy density.

Following a diet that is high in nutrient density and low in energy density is essential for good health. This is the origin of my health equation H = N/C (Health = Nutrients per Calorie). A high ratio of micronutrients to calories is the basis of a healthful diet.

How energy density might promote cancer

Obesity contributes to cancer in a variety of ways: for example, excess fat tissue causes a state of low-grade inflammation, promotes insulin resistance, and produces estrogen.^{1, 3-5} ⁶ However, calorie-rich junk food has effects – other than weight gain – that could contribute to cancer development:

Elevated insulin and IGF-1 levels: From high-glycemic processed foods and high animal protein foods, respectively. Excess of these pro-growth hormones is linked to an increased risk of several cancers.⁴
Oxidative stress and inflammation.⁷
Nutrient inadequacies: ⁸ Many Americans do not meet recommended intakes of magnesium, calcium, vitamin C, vitamin E, and vitamin K.⁹
Lack of protective phytochemicals from natural plant foods (such as glucosinolates from cruciferous vegetables and lignans from flax and chia seeds).^{10, 11}
Excess folic acid from fortified refined foods: Anyone in the U.S. who eats a typical diet (especially those who also take a conventional multivitamin) is exposed to excessive amounts of folic acid due to mandatory fortification of refined grain products. Although rates of neural tube defects have gone down, there are serious concerns about the potential cancer-promoting effects of exposing the whole population to synthetic folic acid daily in the food supply. ^12-15 (Read more: Folate Position Paper)

When you eat a diet with more micronutrients and fewer calories, you age more slowly, and also improve immune system protection against cancer. When you eat excess calories, especially excess calories that do not contain a significant micronutrient load, you accelerate aging and increase your risk of cancer. You can exercise off those extra calories, but they will still negatively affect your health. It is not enough to be at a healthy weight – you must actually eat healthfully to age more slowly, prevent cancer, and live a long healthy life.