Monday, September 17, 2007

intermittent fasting shrinks fat cells?

When I have posted previously about intermittent fasting (IF) it has been about the fast5 / the Warrior Diet style of fasting, i.e., a compressed eating window. You fast or undereat for say 20 hours and you eat during the remaining 4 hours.

There is however another approach to IF - alternate day fasting. Eat one day and fast the next - the approach taken by people like Steve Mount. Or the QOD diet.

Well a new study has just come out looking at this type of IF, with some interesting findings and implications:

* Alternate-day fasting: How good is it for your health?

Researchers report that fasting or eating half as much as usual every other day may shrink your fat cells and boost mechanisms that break down fats.

Consuming fewer calories and increasing physical activity is usually what people do to lose weight and stay healthy. But some people prefer to adopt a diet which consists of eating as much as they want one day while fasting the next. On each fasting day, these people consume energy-free beverages, tea, coffee, and sugar-free gum and they drink as much water as they need. Although many people claim that this diet, called alternate-day fasting (ADF), help them lose weight and improved their health, the effects on health and disease risk of ADF are not clear.

Krista Varady and colleagues studied the effects of alternate-day fasting on 24 male mice for four weeks. To assess the impact of ADF on the health of the mice, the scientists not only tested mice that followed and didn’t follow an ADF diet, but they also studied mice that followed the diet only partially: a group of mice consumed 50 percent of their regular diet every other day (ADF-50%) and another consumed 75 percent of their regular diet every other day (ADF-25%).

The scientists noticed that the mice that followed the complete ADF diet (ADF-100%) lost weight and that the fat cells of both the ADF-100% and ADF-50% groups shrunk by more than half and by 35 percent, respectively. Also, in these two groups of mice, fat under the skin – but not abdominal fat – was broken down more than in mice that did not follow the diet.

These results suggest that complete and modified ADF regimens seem to protect against obesity and type 2 diabetes but do not result in fat or weight loss.

The abstract of the study is below:

Effects of modified alternate-day fasting regimens on adipocyte size, triglyceride metabolism, and plasma adiponectin levels in mice

Calorie restriction (CR) affects adipocyte function and reduces body weight. However, the effects of alternate-day fasting (ADF) on adipose biology remain unclear. This study examined the effects of ADF and modified ADF regimens on adipocyte size, triglyceride (TG) metabolism, and adiponectin levels in relation to changes in body weight and adipose mass. Twenty-four male C57BL/6J mice were randomized for 4 weeks among 1) ADF-25% (25% CR on fast day, ad libitum on alternate day), 2) ADF-50% (50% CR on fast day), 3) ADF-100% (100% CR on fast day), and 4) control (ad libitum). The body weight of ADF-100% mice was lower than that of the other groups (P < 0.005) after treatment. Adipose tissue weights did not change. Inguinal and epididymal fat cells were 35–50% smaller (P < 0.01) than those of controls in ADF-50% and ADF-100% animals after treatment. Net lipolysis was augmented (P < 0.05) in ADF-100% mice, and the contribution from glyceroneogenesis to {alpha}-glycerol phosphate increased in ADF-50% and ADF-100% mice, whereas fractional and absolute de novo lipogenesis also increased in ADF-50% and ADF-100% animals, consistent with an alternating feast-fast milieu. Plasma adiponectin levels were not affected. In summary, modified ADF (ADF-50%) and complete ADF (ADF-100%) regimens modulate adipocyte function, despite there being no change in body weight or adipose tissue weight in the former group.

1 comment:

Chris said...

Just found another alternate day fasting model that might interest some: