Does 16:8 fasting work? A study compares its effects with other popular diets and fasting methods.
This is what you should know. Photo: iStock
Intermittent fasting has become popular for promising weight loss without the need to severely restrict calories on an ongoing basis.
This eating pattern is based on alternating periods of eating with periods of fasting, following a specific schedule. Its main modalities are:
- Time-restricted eating: such as the 16:8 method, which involves fasting for 16 hours and eating only during an 8-hour window.
- Alternate-day fasting: involves not consuming calories for 24 hours in between.
- Full-day fasting: such as the 5:2 diet, where you restrict your intake on two days a week and eat normally on the other five.
Although these strategies are gaining acceptance, there is still uncertainty about whether they actually offer greater benefits compared to traditional diets based on constant calorie restriction or unlimited eating.
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This is what you should know. Photo: iStock
A team of researchers analyzed 99 randomized clinical trials involving 6,582 adults (average age 45 years and 66% women) to compare the effects of different types of intermittent fasting versus restricted or unrestricted diets.
The average duration of these trials was 12 weeks, although some extended to 52 weeks. It's worth noting that the average body mass index (BMI) of participants was 31, and nearly 90% had preexisting health conditions.
The findings showed that both intermittent fasting and continuous calorie restriction achieved similar reductions in body weight. According to the analysis conducted by the University of Toronto's Temerty Faculty of Medicine and published in The BMJ , “Intermittent fasting diets have similar benefits to continuous energy restriction for weight loss and cardiometabolic risk factors.”
Among the methods evaluated, alternate-day fasting was the most successful, with a mean difference of -1.29 kg compared to continuous calorie restriction. It was also more effective than time-restricted feeding and full-day fasting, with mean differences of -1.69 kg and -1.05 kg, respectively.
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Despite the differences found between methods, the study authors clarify that "these differences did not reach the minimally important clinical threshold of at least 2 kg of weight loss for people with obesity."
That is, although alternate-day fasting was highlighted, the benefits were not high enough to be considered clinically substantial.
This is what you should know. Photo: iStock
The researchers also examined the effects on lipids and glucose. Alternate-day fasting showed lower levels of total cholesterol and LDL ("bad") cholesterol compared to calorie restriction, although no benefits were seen on blood glucose levels or HDL ("good") cholesterol with either strategy.
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Trials with follow-up of less than 24 weeks yielded similar estimates, while those of longer duration only demonstrated significant differences in weight loss between those following some type of diet versus those without any dietary control.
Despite the findings, the authors cautioned about several methodological limitations: “High variation (heterogeneity) among dietary strategy comparisons, small sample sizes in many included trials, and low to moderate certainty of the evidence for most of the outcomes investigated.”
Some people turn to intermittent fasting to regulate their metabolism. Photo: iStock
Still, the analysis is one of the first systematic reviews to include direct and indirect comparisons of all the strategies evaluated, which, according to the authors, "allows for more precise estimates."
For this reason, the researchers conclude: "Current evidence indicates that intermittent fasting diets have similar benefits to continuous energy restriction for weight loss and cardiometabolic risk factors. Larger trials are needed to corroborate these findings."
*This content was rewritten with the assistance of artificial intelligence, based on information from Europa Press, and reviewed by the journalist and an editor.
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