Intermittent fasting: Does a brand new examine present downsides — or not?


Intermittent fasting (IF) is an strategy to consuming primarily based on timing. The thought is that fasting for lengthy sufficient permits insulin ranges to fall low sufficient that our physique will use fats for gasoline. Rising proof in animals and people reveals that this strategy results in important weight reduction. When mixed with a nutritious, plant-based weight loss plan and common bodily exercise, IF might be a part of a wholesome weight reduction or upkeep plan, as I described in an earlier blog post.

Now, a randomized controlled trial printed in JAMA claims that IF has no important weight reduction profit and a considerable detrimental impact on muscle mass. Information shops picked up the story and ran headlines like A Potential Downside of Intermittent Fasting and An Unintended Side Effect of Intermittent Fasting.

However what did this examine truly take a look at and discover?

Within the examine, 141 sufferers had been randomly assigned to 12 weeks of both a time-restricted consuming plan (TRE) that concerned fasting for 16 hours and consuming solely throughout an eight-hour window of the day, or a constant meal timing (CMT) consuming plan, with three structured meals a day plus snacks.

Neither group acquired any diet schooling or behavioral counseling, nor was bodily exercise beneficial. There was no true management group (that means a bunch that didn’t obtain any directions about meal timing).

Curiously, each teams misplaced weight. Given the headlines, I needed to learn and reread the outcomes a number of occasions, as a result of they present that the IF group misplaced a statistically important quantity of weight from starting to finish — which wasn’t true within the CMT group. The researchers reported: “There was a major lower in weight within the TRE group (−0.94 kg; 95% CI, −1.68 kg to −0.20 kg; P = .01) and a nonsignificant lower in weight within the CMT group (−0.68 kg; 95% CI, −1.41 kg to 0.05 kg; P = .07).”

Translated into plain English, the IF group misplaced extra weight than might be as a result of likelihood: between half a pound and 4 kilos, or a mean of two kilos. The structured meals group additionally misplaced some weight, though the quantities misplaced might have been as a result of likelihood: between 0.1 and three kilos, or a mean of 1.5 kilos. The upshot was that there wasn’t a major distinction in weight change between the 2 teams. And the researchers noticed a lack of muscle mass within the IF group that didn’t happen within the CMT group.

Diving deeper into the examine

By the way in which, all of those of us might have been consuming fried or quick meals, and sugary sodas and sweet — we don’t know. The examine doesn’t point out high quality of weight loss plan or bodily exercise. This isn’t how IF is meant to be executed! And but the IF of us nonetheless misplaced between half a pound and 4 kilos.

Importantly, the structured meals group additionally misplaced weight. Whereas not important sufficient to show it was as a result of this intervention, for some contributors it was sufficient to make structured meal weight reduction differ little from IF weight reduction. However give it some thought: structured meals are an intervention. In spite of everything, some individuals eat greater than thrice a day, consuming a number of small meals all through the day. Telling individuals to restrict their consuming to a few mealtimes plus snacks may very well be serving to some to eat much less.

The authors very nicely might have concluded that IF was certainly profitable. They may additionally name for a follow-up examine with a real no-intervention management group, in addition to behavioral counseling, steerage on a nutritious diet, and beneficial exercise ranges for IF and CMT teams.

Does further assist make a distinction?

Prior research of IF which have supplied behavioral counseling, and steerage on diet and exercise, have undoubtedly proven optimistic outcomes. For instance, in a previous blog post I described a 2020 American Journal of Scientific Diet study through which 250 obese or overweight adults adopted certainly one of three diets for 12 months:

  • IF on the 5:2 protocol, which suggests drastically decreasing meals consumption for any two of 5 days of the week (right down to 500 energy for girls and 700 energy for males)
  • Mediterranean, which emphasised vegetables and fruit, legumes, nuts, seeds, complete grains, and olive oil with average fish, hen, eggs, and dairy, and with an allowance of 1 glass of wine per day for girls and two per day for males
  • Paleo, which emphasised vegetables and fruit, animal proteins, coconut merchandise, butter, and olive oil, together with some nuts, seeds, and legumes.
  • And that is key: all contributors had been supplied schooling on behavioral methods for weight reduction, stress administration, sleep, and train.

Everybody misplaced weight. The IF group misplaced greater than anybody with a mean of 8.8 kilos, Mediterranean subsequent at 6.2 kilos, and Paleo final at 4 kilos. Adherence was higher with the Mediterranean weight loss plan (57%) and IF (54%) than with the Paleo weight loss plan (35%), and higher adherence resulted in a single to a few kilos extra weight reduction. The Mediterranean and IF teams additionally noticed important drops in blood stress, one other good outcome.

What concerning the loss in muscle mass that occurred within the IF group within the JAMA examine? Whereas this must be studied additional, it’s vital to notice that other research on IF that included guidance on physical activity didn’t present any lack of muscle mass.

The underside line

What’s the takeaway right here? A high-quality weight loss plan and loads of bodily exercise — together with resistance coaching — are crucial for our good well being, and nothing replaces these suggestions. IF is merely a instrument, an strategy that may be fairly efficient for weight reduction for some of us. Whereas this one detrimental examine provides to the physique of literature on IF, it doesn’t reverse it. We merely want extra high-quality research in an effort to have a greater understanding of the way to most successfully incorporate IF right into a wholesome way of life.

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