Intermittent fasting for weight loss: Two types work, according to new review

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  • Intermittent fasting can be effective for weight loss, researchers have shown.
  • Studies found that the method can also improve cardiovascular health.
  • According to a new review, two versions of this diet have significant benefits.

Intermittent fasting, which entails switching between periods of fasting and periods of unrestricted eating, has become an increasingly popular approach to weight loss. Unlike most diets that focus on what you eat, intermittent fasting focuses on when you eat.

The diet comes in a number of guises and, according to a new review, two methods in particular show clear benefits.

The researchers looked at several randomised clinical trials – the "gold standard" of clinical trials – and found that not only can intermittent fasting help with weight loss, but it can also improve metabolic and cardiovascular health.

Writing in the journal JAMA Network, the authors said: "Our findings suggest that intermittent fasting is associated with successful weight loss and metabolic benefits among adults with obesity."

The two intermittent fasting versions they highlighted as having the most statistically significant effect on weight loss were the modified alternate-day fasting (MADF) and the 5:2 diet.

MADF and 5:2 diets

The MADF approach is based on the idea that you fast for one day and eat the next. On the days you fast, you’re allowed a limited calorie intake of around 25% of your calorie needs. On the days you "feast", you should consume around 125% of your calorie needs. 

The 5:2 diet is the most popular intermittent fasting diet. Here, five days of the week involve normal eating days, and on the other two days, calories are restricted to 500–600 per day.

Reviewing the studies

The researchers reviewed 11 meta-analyses, which summarised the results from 130 randomised clinical trials looking at the impact of four intermittent fasting methods on metabolic and cardiovascular health.

Overall, intermittent fasting was found to have associations with weight loss, lower body mass index (BMI), as well as improvements in blood pressure, blood glucose levels, insulin sensitivity and cholesterol levels.

While the MADF and 5:2 diet showed a weight loss of more than 5% in overweight or obese people, the other two approaches (zero-calorie alternate fasting diet and time-restricted diet) did not show the same benefits.

Limitations

The authors pointed out certain limitations of their review, including that most of the analyses studied assessed only the short-term safety of intermittent fasting. They added that the safety and efficacy of these fasting schedules need to be tested across diverse groups of people.

But, to their knowledge, theirs is the first umbrella review that honed in on potential obesity-related health outcomes associated with different types of intermittent fasting.

Since evidence-based support for intermittent fasting is limited, these findings, the authors added, are crucial because they can be used to generate recommendations for doctors and the general population. 

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