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  • Khushboo Pareek

Calorie intake, not intermittent fasting, determines weight loss, claims study

Intermittent fasting, also known as time-restricted eating, may help people in losing weight, but not because of the reasons often cited, such as a change in metabolism, a study has claimed.

Contrary to previous hypotheses that suggested metabolic changes or circadian rhythms played a significant role, the study published on Friday in Annals of Internal Medicine, suggests that the primary reason behind weight loss during intermittent fasting may simply be a reduction in overall calorie intake.

The conclusion stems from a randomized-controlled trial, where individuals following a time-restricted diet lost a similar amount of weight compared to those on a non-restricted diet.

The study, spearheaded by Nisa Marisa Maruthur, an internal medicine specialist at Johns Hopkins, has its own constraints and, like any single study, doesn't provide the final conclusion on the topic.

However, according to nutrition experts Krista Varady and Vanessa Oddo from the University of Illinois, who penned an editorial alongside the study, it brings us a step closer to understanding the mechanisms behind time-restricted eating, or TRE.

Maruthur and her team demonstrated that TRE is effective for weight loss simply because it helps individuals consume fewer calories.

The study included 41 participants, with 21 adhering to a time-restricted diet for 12 weeks, while the remaining 20 individuals maintained their usual eating pattern.

After the 12-week period, both groups experienced similar weight loss, averaging around 2.4 kg (5.3 pounds), with no significant difference between them, according to the researchers. There were also no noticeable distinctions between the two groups in terms of glucose control, waist size, blood pressure, or lipid levels.

The study concluded, "In the setting of isocaloric eating, TRE did not decrease weight or improve glucose homeostasis relative to a UEP, suggesting that any effects of TRE on weight in prior studies may be due to reductions in caloric intake."

"Our results indicate that when food intake is matched across groups and calories are held constant, TRE, as operationalized in our study, does not enhance weight loss," Maruthur and her colleagues concluded

Although some experts applauded the study, they also averred that it's not surprising. "The headline finding that TRE does not magically lead to more weight loss sounds sensational but is also obvious," Adam Collins, a nutrition expert at the University of Surrey, said.

Naveed Sattar, a professor of cardiometabolic medicine at the University of Glasgow said, the conclusion "tells us what we expected—that there is nothing magical about time-restricted eating on weight change other than effects to reduce caloric intake."

He added, "If time-restricted eating helps some people eat less calories than they would otherwise, great."

Varady and Oddo, however, viewed it as a positive development for individuals aiming to shed pounds. They noted that many patients abandon conventional diets, like daily calorie restriction, due to the frustration of constantly monitoring food intake.



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