A review of controlled trials has found little evidence that intermittent fasting is a superior long-term weight loss approach.

Intermittent fasting diets have gained a lot of attention. Popularised by Dr Michael Mosley’s 5:2 Fast Diet, the concept involves eating normally, but sensibly, for five days a week and, on the other two days, cutting energy intake to 500 Calories for women and 600 Calories for men.

There are endless variations of fasting diets which can involve true 24 hour fasts where only water is consumed, to alternate day fasting and feasting, to even just selected times of the day when eating is allowed.

Intermittent fasting is not a new weight-loss fad; it has been part of some health and religious practices, such as Ramadan, for thousands of years.

So what does research say about the health outcomes of fasting, in particular as an approach for weight loss?

Intermittent fasting can work for weight loss in the short term at least but what really counts is how weight loss can be maintained for the long term.

A recent systematic review and meta-analysis looked at weight and metabolic outcomes from controlled trials where some form of intermittent fasting was used for periods greater than six months.

All up, there were six studies that could be examined which involved comparing intermittent fasting against some form of traditional calorie-restriction diet. The difference in weight loss between the two approaches was negligible at just 100 grams.

The rates of adherence to the diet interventions were also similar between compared groups. Any favourable changes in levels of blood lipids, glucose or insulin were not significantly different between an intermittent fasting approach and a continuous energy restriction diet approach.

The findings here are certainly not surprising. With so many diet comparison studies published, the clear finding is that no one approach is a stand-out success when realistic longer-term timeframes are considered.

All forms of energy restriction can work for weight loss but it is sustaining the approach chosen and maintaining weight loss that is by far the most difficult hurdle to overcome.

Implications

At its heart, intermittent fasting is just a form of energy restriction. It can work for some, but is certainly not for everyone and nor too do the individual stories of success mean that everyone else should consider adopting it for weight loss.

Last Reviewed: 14/10/2019

© Norman Swan Medical Communications.



References

Headland M et al. Weight-loss outcomes: a systematic review and meta-analysis of intermittent energy restriction trials lasting a minimum of 6 months. Nutrients 2016;8:354.