A combination of a healthy diet and exercise lowers angiogenesis-related proteins that promote cancer cell growth and survival.
The study, published in the journal Cancer Research, found a reduction in the levels of a blood protein involved in angiogenesis when overweight and obese women experienced weight loss through diet and exercise.
Angiogenesis is the process by which damaged blood vessels are repaired and new blood vessels are formed.
Without oxygen and nutrients, both healthy cells and cancer cells cannot survive. These cells send out signals, called angiogenic factors, and it is these factors that encourage new blood vessels to grow and cancer cells to grow into a tumor.
Tumors are unable to grow beyond a few millimeters in size without a blood supply. However, once cancer cells stimulate the growth of a blood vessel, they can develop quickly.
Catherine Duggan, Ph.D., principal staff scientist in the Public Health Sciences Division at the Fred Hutchinson Cancer Research Center in Seattle, WA, explained that researchers have suggested that preventing angiogenesis can prevent tumor cell growth.
She continues to say that although this "angioprevention" may work as a strategy to prevent cancer in healthy individuals, the drugs involved in blocking this process have potential adverse effects, which restricts their use in preventing cancer.
"We know that being overweight and having a sedentary lifestyle is associated with an increase in risk for developing certain types of cancer. However, we don't know exactly why. We wanted to investigate how levels of some biomarkers associated with angiogenesis were altered when overweight, sedentary, postmenopausal women enrolled in a research study lost weight and/or became physically active over the course of a year."
Catherine Duggan, Ph.D., Fred Hutchinson Cancer Research Center
Along with senior author of the study Anne McTiernan, M.D., Ph.D., and colleagues, Duggan measured the effect of diet and exercise on the circulating levels of angiogenesis-related proteins - VEGF, PAI-1, and PEDF - in the blood of study participants at baseline and 12 months.
Blood samples were taken from 439 postmenopausal, overweight, and obese women who were considered healthy and sedentary and aged 50-75.
These participants were split into four groups:
- Calorie restriction diet group - intake of no more than 2,000 kcal per day that included less than 30 percent of fat calories
- Aerobic exercise group - performing 45 minutes of moderate to vigorous exercise 5 days a week
- Combined diet and exercise group
- The control group (no intervention).
Higher weight loss linked with greater reduction in proteins
The researchers found that after 12 months of intervention, the women in the diet, exercise, and combined diet and exercise groups lost on average 8.5, 2.4, and 10.8 percent of body weight, respectively. This loss was considerably higher than the average of 0.8 percent in the control group.
They also found that after 12 months, the participants in the diet and combined diet and exercise groups had significantly lower levels of the angiogenesis-related proteins than the control group. These lower levels were not observed in the aerobic exercise group.
"Our study shows that weight loss is a safe and effective method of improving the angiogenic profile in healthy individuals. We were surprised by the magnitude of change in these biomarkers with weight loss," says Duggan.
A linear trend was seen in the reduction in angiogenesis-related proteins, which showed that the higher the amount of weight loss the women experienced, the greater the reduction in protein levels.
"While we can't say for certain that reducing the circulating levels of angiogenic factors through weight loss would impact the growth of tumors, it is possible that they might be associated with a less favorable milieu for tumor growth and proliferation," Duggan notes.
Duggan adds that although exercise is important to prevent weight gain, and to maintain weight loss, exercise alone does not have a significant effect on the amount of weight lost by an individual.
"Our study shows that making lifestyle changes - in this case, simple changes to the diet to reduce weight - can lower the risk factors for cancer," Duggan concludes.
Study limitations include that only three angiogenic factors were measured and that although biomarkers were measured in circulating blood, they were not measured in other tissues such as adipose.