The Evidence on
Fasting For Weight Loss
Moderate Alternate Day Fasting (MADF)
According to the Fast Track Trial Team,
“Modified alternate day fasting (MADF), has shown success in adults.”
This is not true.
While fasting has become more popular in recent years, there is nowhere near enough evidence to say that it has lasting benefits for adults for either lasting weight loss or health improvements.
In order to claim that a weight loss intervention 'works', we need to look at long-term research. This is because there is a lot of research to show that on weight loss diets, almost anything 'works' in the short term, but the same pattern happens regardless of the type of diet chosen.
About 6 months to 1 year after any diet, people tend to regain the weight. In order to say that a diet really 'works', we need to look beyond the short-term research and examine the long-term benefit. This means looking at what happens to people 2 - 5 years after going on a diet.
There is very little long-term research on moderate alternate day fasting or intermittent fasting diets in adults. A 2016 review of intermittent fasting trials identified just six studies with a follow up or 12 months or longer.
Only 2 of these were similar to an alternate day fasting regime, and the results were not glowing.
A 2014 study reported an intervention on older females (average age of 60), in which participants undertook either an IER regime where they restricted for 1 week and then ate normally the following week, and compared them to continuous energy restriction (CER) group.
40% of the study participants had dropped out by the 8 week mark, indicating that the regimes were difficult to stick to.
Only 36 finished the 12 month period, and of these, just 11 (7 in the IER and 4 in the CER) people reported continuing to stick to the diets.
The trial reported only modest weight losses at 12 months (@4kg in the CER group and @2kg in the IER group), with no statistical differences between the two diet conditions. Thus, in this trial, fasting was not found to be any different to garden variety dieting.
Another long term study on fasting diets in men with Type 2 diabetes found small weight and biomarkers improvements were noted initially, however by 18 months later none of these changes were maintained and all participants were back to baseline.
A 2017 randomised controlled trial (RCT) on fasting directly compared a fasting group h a ‘standard’ calorie controlled diet (this trial is similar to the structure of the Fast Track trial). This RCT had a 12 month follow up period, and the results did not support the superiority of MADF over everyday dieting. The authors concluded that:
“Alternate-day fasting did not produce superior adherence, weight loss, weight maintenance, or cardioprotection vs daily calorie restriction.” (p.937)
In addition to not being effective, the fasting group had a higher drop out rate (38%) than the standard calorie restriction group (29%), indicating that subjects in this group found the intense restriction harder to follow. Compared to the calorie restriction group, those in the fasting group also developed disturbed eating behaviours:
“Participants in the alternate-day fasting group ate more than prescribed on fast days, and less than prescribed on feast days, while those in the daily calorie restriction group generally met their prescribed energy goals.” (p.930)
It is of great concern that a trial subjecting adolescents to such an extreme dieting regime as alternate day fasting has been granted ethical clearance given the scientific evidence from preceding long term adult trials which show no evidence of superior efficacy over traditional dieting methods, and a return to baseline by 18 months.
Moreover, the evidence from the RCT which is very similar to the Fast Track protocol, showed not only that the intervention was no better than standard calorie restriction, but that participants in the IF group found adherence more difficult, and that it was associated with disturbed eating behaviours.
With no evidence of 'success' in MADF or IF in adults, it is unethical to test the theory that it might be beneficial for teenagers. Our kids are not guinea pigs.
Please sign the petition to Stop The Fast Track Trial
What About Less Extreme Diets?
Obviously, fasting is no different to any other kind of diet for weight loss. Why not choose another, less extreme diet? Is that a better choice for your teenager?
There is an enormous amount of research to show that all diets result in a small amount of weight loss (usually less than 5kg) in the short term, and that this weight loss is followed by weight regain.
The evidence of weight regain following modest weight loss is extremely strong - classified as "Level A" (the strongest you can get) - by the NH&MRC. The Fast Track researchers' own published research on their less extreme diets shows that the teenagers subjected to such regimes ended up regaining all of the weight loss by 2 year follow up.
We must acknowledge science: weight loss dieting is not effective, and runs the risk of teaching vulnerable adolescents disordered eating behaviours. Rather than sending your child down the ineffective and harmful path of dieting for weight loss, explore safe alternatives such as those encouraged by the American Academy of Paediatrics:
"Discourage dieting, skipping of meals, or the use of diet pills; instead, encourage and support the
implementation of healthy eating and physical activity behaviors that can be maintained on an ongoing basis. The focus should be on healthy living and healthy habits rather than on weight.”
For more information, head to "The Alternatives" for details on other ways to help your child.