A small study carried out at the University of Illinois suggests that on-off fasting (fasting on alternate days) may help obese people to lose weight and to lower their cholesterol levels.
The study, of 12 women and 4 men, all obese, was led by Dr. Krista A. Varady and colleagues at the University of Illinois at Chicago. It has been published in the American Journal of Clinical Nutrition as Short-term modified alternate-day fasting: a novel dietary strategy for weight loss and cardioprotection in obese adults.
As the title indicates, this sort of diet is a novel one - not something that dieters normally consider, or that doctors normally recommend. The participants in the study were instructed to eat normally on their feed days, and to eat just 25% of their maintenance calories between 12pm and 2pm on their fast days.
On average, participants lost around 12 lbs in eight weeks. They also saw other health benefits: the New York Times explained that:
At the end of the eight-week diet, their total cholesterol had dropped by 21 percent, on average, while their LDL cholesterol had dropped 25 percent. Moreover, their systolic blood pressure (the upper number in a blood pressure reading) had fallen by an average of five points.
The participants ate around 100-125% of their maintenance calories on feed days, so did not overcompensate for the fast days. Dr Varady suggested to the New York Times that their stomachs kind of shrunk, so they were satisfied with less food.
Should we all be fasting to lose weight?
It's important to note that this was an extremely small study - just sixteen people - and so the results are not necessarily representative. Also, the individuals involved were all obese (BMI over 30), so if you have less weight than that to lose, this sort of diet could be inappropriate.
On-off fasting may well work for some people, but don't try it without consulting your doctor first.