Role of obesity, calories & exercise in breast cancer

Role of obesity, calories & exercise in breast cancer

- Claire Sowerbutt
Obesity, as you're no doubt aware, is a fairly hot topic these days - for a variety of health-related reasons. For example, it is known to lead to chronic illnesses including heart disease and diabetes, which are currently on the rise at epidemic rates in North America. However, obesity is now believed to play a critical role in the development of breast cancer. Diet - as in how much and how often we eat affects development of breast tumors. Not surprisingly, perhaps, exercise is tied into this.

A study done at the National Cancer Institute (NCI, United States), presented during the American Association for Cancer Research meeting this October shows that calorie restriction or occasional fasting inhibits Breast Cancer growth. The study was done in mice, some of which were provided with an unlimited food supply. They rapidly became obese and developed fatal mammary tumors. However, the second group of mice that received a lower calorie intake, or fasted one day per week, lived tumor-free two to three times longer than the obese mice.

In a similar vein, a study done at the University of Minnesota shows that periodic calorie restriction - rather than a constant low calorie diet - may provide greater protection against breast cancer. In other words, the way we eat has an impact, as well as how much.

This study also used mice. They were fed on a "food as desired" basis, on an intermittent basis, or on a caloric restriction/refeeding diet. The results showed an 84% incidence of breast tumors in the mice that ate without restriction, a 37% incidence in the mice that had calorie restrictions, and a 15% incidence of breast tumors in the mice who had an intermittent caloric restriction/refeeding program. The study investigators also found that the mice that ate as they wanted died at a younger age than the mice in the other two groups.

While these studies seem to indicate that controlling calorie intakes plays a role in cancer prevention, researchers at the NCI stress the subsequent importance of exercise. Why? Well, calorie restriction reduces the amount of insulin-like growth factor - IGF-1 - by as much as 50%. IGF-1 helps to regulate aspects of development and aging - such as bone density. Calorie restriction can result in a decrease in bone density, which can lead to osteoporosis -a significant health problem in post-menopausal women - the same demographic who are increased risk for breast cancer. Exercise helps to minimize the loss of bone density - weight-bearing exercise can help build bone strength.

Further dietary studies will continue, and no doubt we will learn a great deal over the coming years. But for now the message seems to be - less is more - at least when it comes to food.

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