Effect of Daily Calorie or Alternate-day Calorie Reductions on Risk for Cardiovascular Disease and Cancer

Overweight individuals are at greater risk for certain chronic diseases such as cardiovascular disease and cancer when compared to those who are normal weight. Dietary restriction has been shown to lower the risk of these chronic diseases in overweight human subjects as well as in normal weight rodents. The majority of studies examining dietary restriction protocols in rodents or humans implement daily calorie restriction (CR), i.e. where the amount of energy consumed is decreased by a certain percentage every day. Another dietary restriction regimen employed, although less commonly, is intermittent caloric restriction, or alternate-day fasting (ADF), i.e. where food is available ad-librium every other day, alternating with a partial or complete caloric restriction day. Recent findings suggest that ADF may modulate certain indices of disease risk to a similar extent as daily CR in animal models. The effect of ADF regimens in comparison with CR regimens on disease risk has yet to be performed in human subjects, however. ADF protocols need not result in weight loss, and would therefore be appropriate for non-obese individuals. Accumulating evidence suggest that adipose tissue may play a role in modulating chronic disease risk by releasing substrates, such as fatty acids, or a variety of hormones, including adiponectin and leptin. The effect of ADF and CR on adipose tissue metabolism and hormone release remains unclear. Accordingly, the aim of the present study is to compare ADF regimes to CR for their effects on risk factors for cardiovascular disease and cancer and their effects on adipose tissue metabolism and hormone secretion, in normal weight to modestly overweight (BMI 22-27 kg/m2) human subjects.

Inclusion criteria

• Male and female; body mass index (BMI) between 20-30 kg/m2;
• Age between 35-65 years; sedentary (light exercise less than 1h per week) or moderately active (1 to 2h per week);
• Weight stable for >3 months prior to the beginning of the study;
• Able to give written informed consent;
• Female subjects must be post-menopausal for at least 2 years and can not be on hormone replacement therapy (HRT).

Exclusion criteria

• Diabetic;
• History of cardiovascular disease, i.e. myocardial infarction or stroke;
• History of cancer;
• Taking glucose lowering medication;
• Taking weight loss medication