In the last few years, intermittent fasting has been linked to various important health functions outside of weight loss.
On balance, the hormone called ghrelin appears to be responsible for the largest share of restricted eating’s benefits.
When released by the stomach, ghrelin stimulates a psychological desire in mammals to work harder–tricking the body into anticipating indefinite periods of struggle. Ultimately, we shed pounds, make the most out of macronutrients, and join the dense company of famous fasting fanatics.The only question that remains relates to duration.
There are many different ways to fast, with the 16:2 and the 5:2 method being the most popular among them. The former requires subscribers to fast every day for 14–16 hours and limit daily eating windows to 8–10 hours while the latter allows followers to eat normally for five days of the week and then restrict calorie intake to 500–600 for two days of the week.
The thing is, longer fasting may not actually make that much difference as far as health benefits are concerned.
At least according to a new study published in the journal Cell Metabolism. The authors more directly posit that four and six-hour time-restricted feeding regimens produce comparable reductions to energy, fat, and insulin resistance and oxidative stress over a two month period.
“Time-restricted feeding (TRF) regimens have grown in popularity; however, very few studies have examined their weight-loss efficacy,” The University of Illinois researchers wrote in the new paper. “We conducted the first human trial to compare the effects of two popular forms of TRF on body weight and cardiometabolic risk factors.”
The participants recruited for the new study, who were all obese, were placed into two groups: the four-hour fasting group and the six-hour fasting group.
Between 1 p.m and 5 p.m, the four-hour group got to eat whatever they liked.
Those in the six-hour group was giving the same criteria between only 1 p.m. and 7 p.m.
The subjects were only allowed water and zero-calorie beverages outside of their eating windows.
“Energy intake was reduced by ∼550 kcal/day in both TRF groups, without calorie counting. These findings suggest that 4- and 6-h TRF induce mild reductions in body weight over 8 weeks and show promise as interventions for weight loss. These diets may also improve some aspects of cardiometabolic health,” the authors continued.
The results yielded no discernable distinction between the two fasting methods. Neither had any impact on cholesterol levels, triglycerides, or blood pressure.
However, both saw participants lose roughly 3% of their body fat, lower levels of oxidative stress, and insulin resistance.
“It’s also telling that there was no added weight loss benefit for people who sustained a longer fast — until we have further studies that directly compare the two diets or seek to study the optimal time for fasting, these results suggest that the 6-hour fast might make sense for most people who want to pursue a daily fasting diet, “concluded lead author Krista Varady in a university release.“The findings of this study are promising and reinforce what we’ve seen in other studies — fasting diets are a viable option for people who want to lose weight, especially for people who do not want to count calories or find other diets to be fatiguing.”