It’s hard not to associate the term “fasting” with a crash diet. And it’s true, the entire concept behind intermittent fasting (IF) is to “starve” the body.
But contrary to popular belief, that’s not actually a bad thing. In fact, it’s your body’s natural state.
Evolutionarily speaking, we were never meant to have an endless abundance of accessible food. Our primitive ancestors only ate when they were able to successfully hunt or forage. They didn’t have refrigerators or grocery stores. And they certainly weren’t able to walk into their local convenience store for a bag of chips at midnight.
So when you think about it, it makes sense that a dietary approach involving frequent periods of fasting would have a long list of metabolic benefits… all without any calorie restriction at all.
Still, seeing is believing. So the results of a new study, recently published in the journal Obesity, should help convert any dieters still in doubt.
Fasting supercharges fat burning
In a small but compelling study, researchers recruited 11 overweight or obese men and women in otherwise good health.
Subjects were randomly assigned to different meal timing plans. One featured three meals during a 12-hour period—with the first meal at 8:00 a.m. and the last meal at 8:00 p.m. The other plan featured three meals over a six-hour period—with the first meal at 8:00 a.m. and the last meal at 2:00 p.m.
Both schedules included the same amount of food and the same types of meals. The only differences were in length of fasting period and timing of the final meal.
Subjects followed their assigned meal plans for four days, after which researchers measured key metabolic factors—including calorie, carb, fat, and protein expenditure—in a controlled environment. They also evaluated levels of appetite and hunger hormones.
And here’s what they found: There was no difference in calorie burning between the typical 12-hour meal schedule group and the early time-restricted feeding group. But the latter group benefited from lower levels of hunger hormones and appetite suppression.
And maybe most notably? They also burned more fat over the course of 24 hours.1
Pick a plan and stick to it
This study’s design matches my own version of IF, which restricts eating to a six-to-eight-hour window—say, between 12:00 p.m. and 6:00 p.m.—on a daily basis.
Of course, that isn’t to say you can eat whatever you want in that time frame. Healthy choices are still important. You simply want to be eating less frequently. (Personally, I only eat once per day—but I know that’s not realistic for everyone.)
Earlier dinners are obviously better too, for much the same reasons. Keeping meals away from your bedtime ensures that your body’s natural circadian rhythms stay aligned, and that your internal clock stays on schedule.
Circadian misalignment paves the path to obesity—regardless of how healthy you eat. (In other words, yes, a midnight salad can still make you fat.)
So, use these two ground rules to design an approach that works best with your lifestyle: Only eat during a six-to-eight-hour window, and stick to a healthy, balanced diet. It might take some getting used to. But clearly, this is one case where the payoff is well worth the effort.
- Ravussin E, et al. “Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans.” Obesity (Silver Spring). 2019 Aug;27(8):1244-1254.