Long-Term Low-Protein, Low-Calorie Diet And Endurance Exercise Modulate Metabolic Factors Associated With Cancer Risk, American Journal of Clinical Nutrition, 2006
Looked at 3 groups of middle-aged (53 +/- 11 years old), nonsmoking, healthy men and women:
- 21 sedentary subjects, low-protein (about 9% of calories), low-calorie (about 2000) diet*
- 21 endurance runners
- 21 sedentary subjects (non-obese), Western diet
- Levels of insulin, free sex hormones, leptin (released from body fat), and C-reactive protein (marker for inflammation) were lower and sex hormone–binding globulin (protective against cancer) was higher in the low-protein, low-calorie diet and runner groups than in the sedentary Western diet group.
- Levels of insulin-like growth factor I (IGF-I) was lower in the low-protein, low-calorie diet group.
"Subjects eating a low-protein, low-calorie diet had much lower plasma IGF-I concentrations and IGF-I:IGFBP-3 than did BMI-matched endurance runners, which suggests that dietary factors may provide additional protective effects, independent of body fat mass."Perhaps this is why Campbell could turn cancer on and off in rats by changing the amount of protein they ate (Liver Cancer: Now You See It, Now You Don't).