Alternate-Day Fasting Shows Promise for Obese Dieters
[Writer] This is research news from U-I-C – the University of Illinois at Chicago. Today Krista Varady, assistant professor of kinesiology and nutrition, talks about a study of obese persons who took part in a diet called alternate-day fasting.
Here’s Professor Varady:
[Varady] Dietary restriction has been shown to help people lose weight and lower heart disease risk. The most common form of dietary restriction is something called calorie restriction, which involves reducing energy needs by 15 to 40% daily. Another form of dietary restriction is something called alternated-day fasting, or ADF. Alternate-day fasting regimes consist of a feed day, where the person can pretty much eat whatever they want, alternated with a fast day where the person is pretty heavily restricted — so they’re only consuming about 25% of their energy needs, or something equivalent to about a lunch.
Alternate-day fasting regimens were created to increase adherence to dietary restriction protocols, since they only require energy restriction every other day, rather than every day as with CR – or calorie restriction. So in this way, even though the person is undergoing a pretty heavy restriction day, they can always look forward to the next day when they can eat whatever they want.
In a recent study published by our group in The American Journal of Clinical Nutrition, we show that ADF is an effective weight loss therapy in obese individuals. This has never been shown before.
Specifically what we did was we had an 8-week intervention period of alternate-day fasting, and we showed that people lost between 10 to 30 pounds after this 8-week period. In the study we also wanted to look at whether these people were able to do the alternate-day fasting on their own at home. So what we was, in the first 4 weeks we basically provided them with the food – about 25% of their energy needs, so a small
lunch. We did this because we wanted to show them basically what kind of portion sizes they should be eating, what kinds of foods they should be eating, and after this 4-week control feeding period, we pretty much set these people free and let them eat whatever they wanted at home – but to still adhere to the dietary restriction protocols, so to still consume about 25% of their energy needs on the fast day.
What we found was that people were actually pretty good at doing this diet on their own at home. We measured this by looking at the weight loss between the controlled feeding phase and the self-selected feeding phase. We found that people lost a pretty consistent amount of weight between the two phases – about 1 to 3 pounds a week. So this shows that people can do it at home.
Another question we wanted to answer was how long does it take people to habituate to this kind of diet? How long does it take for them to no longer feel hungry on the fast day? We showed that after about 2 weeks or so, people stopped feeling hungry pretty much on the fast day, so their bodies became habituated to it.
Lastly, what our study showed was that ADF may be promising to reduce heart disease risk in obese individuals. Specifically, after 8 weeks of diet, we saw that the “bad” cholesterol, LDL, was decreased along with reductions in triglycerides, blood pressure and heart rates. And since these are all key risk indicators of heart disease, ADF may not only help people lose weight but also help them decrease their risk of coronary events.
Alternate-day fasting is not a very well studied area. There have only been about 3 or 4 human studies done, to date. So there are still many questions that we’d like to answer. Some of the things our group would like to answer are, who can actually benefit from this diet? Would it be the majority of the population, or is it only good for certain people who can self-monitor, or really do this on their own at home? Another question we have is can this diet be used to help people maintain their weight loss? So once they’re lost their weight and achieved their healthy weight loss goal, can they stick to it for the long term, and if they can’t, what happens when they go off the diet? Do they just gain the weight right back – what happens there? So we’re hoping to run studies testing these questions in the next couple of years.
In conclusion, our results show that ADF is a promising diet strategy for weight loss and heart disease prevention in obese adults. Additionally, we show that ADF can be self-implemented at home, thus is an effective strategy even when removed from a clinically- controlled environment.
[Writer] Krista Varady is assistant professor of kinesiology and nutrition.
For more information about this research, go to www.today.uic.edu … click on “news releases.” … and look for the release dated November 4, 2009.
This has been research news from U-I-C – the University of Illinois at Chicago.
