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June 27, 2023

Intermittent fasting can be as effective for weight loss as counting calories, study finds

While restricting daily eating to a window of time can help people shed pounds, experts caution that for some it can raise the risk of developing eating disorders

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Intermittent Fasting Study Kirill Tonkikh/Unsplash

Intermittent fasting focuses on when people eat rather than how much they eat. Research indicates that it may be as effective as calorie counting for weight loss.

Between frequent advertisements about weight loss strategies, programs and supplements, intermittent fasting is often pushed aside as a temporary fad. But new research suggests that time-restricted eating can be just as effective for weight loss as counting calories. 

In a study published in the Annals of Internal Medicine, researchers found that limiting food intake to a small time window was just as effective as calorie counting for losing weight. The study, which involved 77 Chicagoans with obesity, separated participants into three groups for six months, asking them to try intermittent fasting (eating between noon and 8 p.m each day), calorie counting (with a 25% reduction in calorie intake compared to normal eating habits) or to make no dietary changes.

After six months, researchers then wanted to see if participants were able to keep weight off; the calorie counters upped their calorie intake and the intermittent fasters expanded their eating window to 10 hours per day.

The researchers found that both dieting groups lost weight in the first six months, maintained weight loss during the next six months and lost 5% of their body weight over the course of a year. Those who tried intermittent fasting consumed 425 fewer calories per day and lost about 10 more pounds than those who did not change their eating habits. Those who counted calories consumed 405 fewer calories per day and lost about 12 more pounds than the control group. 

"We really wanted to see if people can lose weight with this over a year," Krista Varady, a professor of nutrition at the University of Illinois Chicago and the author of the study, told NPR. "Can they maintain the weight loss? The key take-away is that you can basically achieve the same amount of energy restriction by counting time instead of counting calories. People usually eat within a 12-14 hour window, so all we're doing is cutting out around six hours." 

Intermittent fasting focuses on when people eat, rather than how much they eat. There are several different methods of intermittent fasting, including alternating days between eating regularly and fasting or cutting down food intake to just eight hours out of the day. 

Previous research has shown that intermittent fasting can provide health benefits like reduced brain fog, decreased risk of developing diabetes, weight loss, improved sleep, lower blood pressure and less inflammation. 

For many, intermittent fasting can help weight management and address chronic conditions like irritable bowel syndrome, high cholesterol and arthritis. Still, intermittent fasting may not be for everyone. 

"There's nothing sort of magical about, 'I'm only going to eat for these eight hours per day,'" Dr. Adam Gilden, an associate professor of medicine at the University of Colorado School of Medicine, told NBC News. "The person doing that strategy still has to pay attention to what types of foods they're eating and the portions and the amounts." 

People who should steer clear of intermittent fasting include children and teens under 18 years old, those who are pregnant or breastfeeding, people with type 1 diabetes who take insulin and those with a history of eating disorders, according to experts at Johns Hopkins. 

Other research has linked intermittent fasting to an increased risk of eating disorder behavior and psychopathy, particularly among young women. Some people may develop a binge eating disorder when experiencing a "rebound effect" after restricting food intake. Experts have long held that suppressing hunger cues can lead to disordered eating, particularly among those with poor body image or people who use food as a coping mechanism. 

Similarly, although counting calories may be effective at promoting weight loss, it is not beneficial for everyone. For those with a history of disordered eating and self-weighing, it may foster or worsen a person's relationship with food and exercise, Healthline reported. 

When considering weight loss strategies, it is important to discuss options with a health care provider to make sure that methods used are the most effective for personal weight loss goals and account for medical concerns or conditions that may be impacted. 

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