Fitting your eating into a small window may lead to large gains in weight loss according to a new study just published. Researchers from the University of Illinois at Chicago found time-restricted eating, also known as intermittent fasting, was effective for losing weight as well as improving insulin resistance and oxidative stress levels.
Scientists conducted a clinical trial comparing participants from two increments of time-restricted eating to a control group. One fasting group limited their eating to a 4-hour window and the other used a 6-hour eating window.
"This is the first human clinical trial to compare the effects of two popular forms of time-restricted feeding on body weight and cardiometabolic risk factors," said Krista Varady, professor of nutrition at the UIC College of Applied Health Sciences.
Those in the 4-hour group were asked to limit their eating to between the hours of 1 p.m. and 5 p.m., while the 6-hour group participants were asked to limit their eating to between 1 p.m. and 7 p.m. There were no restrictions on what they could eat during the prescribed eating window, but during the fasting hours they were limited to just water or calorie-free beverages.
The control group was instructed to maintain their weight. They were asked to not make any changes to their diet or their physical activity levels.
All study participants were followed for 10 weeks and underwent several tracking measurements. They were checked for weight, insulin resistance, oxidative stress, blood pressure, LDL cholesterol, HDL cholesterol, triglycerides and inflammation.
Researchers found participants in the fasting groups each reduced their calorie intake by about 550 calories each day just by sticking to their respective eating windows. That resulted in a loss of about 3% of body weight over the 10 weeks. While there were no changes in blood pressure, cholesterol or triglycerides levels, the fasting group participants were able to reduce their insulin resistance and oxidative stress levels.
Interestingly, there was no significant difference between the 4 and 6-hour fasting group participants when it came to weight loss or cardiometabolic risk factors.
"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," Varady said. "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."