Intermittent fasting, specifically time-restricted eating, may be a safe and viable weight loss tool for adults with obesity. Results may lead to naturally decreased caloric intake, according to Kelsey Gabel Clinical Assistant Professor, College of Applied Health Sciences.
The study reported results from a clinical trial that compared a 4-hour time-restricted feeding diet and a 6-hour time-restricted feeding diet to a control group. In both the study groups, patients were allowed to eat whatever they wanted during the 4-hour or 6-hour eating period. During the fasting hours, participants were directed to only drink water or calorie-free beverages. In the control group, participants were directed to maintain their weight and not change their diet or physical activity levels.
The participants were followed for 10 weeks as weight, insulin resistance, oxidative stress, blood pressure, LDL cholesterol, HDL cholesterol, triglycerides and inflammatory markers were tracked.
The study, published in Cell Metabolism, found that participants in both daily fasting groups reduced calorie intake by about 550 calories each day simply by adhering to the schedule and lost about 3% of their body weight. The researchers also found that insulin resistance and oxidative stress levels were reduced among participants in the study groups when compared with the control group. There was no effect on blood pressure, LDL cholesterol, HDL cholesterol or triglycerides.
The findings of this study are promising and reinforce what has been 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. It’s also telling that there was no added weight loss benefit for people who sustained a longer fast, these results suggest that the 6-hour fast might make sense for most people who want to pursue a daily fasting diet.”
There were no major adverse health events reported by study participants during the study and that the mild adverse events — such as dizziness or headaches — were limited to the beginning of the trial.
Intermittent fasting has become a “giant umbrella term” encompassing several different types of eating plans, Gabel said. Alternate-day fasting is defined as eating between zero and 25% of energy needs on a “fast” day, and eating ad libitum on a “feast day.” A “5:2” diet is an eating plan with 1 to 2 typically nonconsecutive fasting days and 5 to 6 days of ad libitum eating within a week. Time-restricted eating is defined as eating all meals within a short window each day, either 8, 6, or even 4 hours. The two most popular versions of time-restricted eating involve an 8-hour window and a 6-hour window of eating. The plans have no calorie restriction guidelines.
Gabel cautioned that intermittent fasting is not for everyone. Pregnant or lactating women, people with disordered eating, shift workers and frequent snackers are not candidates for an eating plan that involves fasting, she said.
It is also important to warn patients starting an intermittent fasting plan that it is challenging in the beginning, she said.
“The first 10 days seem to be the most difficult for our participants, and that is true of any diet,” Gabel said. “The most common complaint is headaches, especially during the first 10 days. Eventually, we’ve been told by our participants anecdotally that you do feel a boost of energy on your fast days.”
Time-restricted eating seems to produce slower weight loss, about 5 to 10 lbs 3 months, but it is easier to follow. You don’t have to count calories. You just have to watch the clock.