New study shows fasting may be as effective as cutting calories

A new study published in Lipids in Health and Disease shows that intermittent fasting may be equally effective as chronic caloric restriction for weight loss, fat loss, and reduction in triglycerides. It also appears to be better for improving insulin resistance markers.

It’s been an amazing few weeks for intermittent fasting and time-restricted eating. Peer-reviewed journals have published three recent trials adding to our growing knowledge base. You can read prior posts about studies just published in JAMA Internal Medicine and The Journal of Clinical Endocrinology and Metabolism and learn about how contradictory studies sometimes help us reassess our inherent beliefs.

Not only do these studies teach us about fasting, but they also teach us the importance of understanding a trial’s design before drawing conclusions. Each of these studies had a different protocol, different measurements, and different conclusions. And each study has its place in our growing body of evidence about intermittent fasting.

In the most recent study, researchers randomized 88 people with overweight or obesity and elevated triglycerides to either chronic calorie restriction (70% of the calculated daily energy needs) or intermittent calorie restriction (eating 100% of calculated needs on four days of the week and 30% on three days).

After eight weeks, both groups lost almost 9 pounds (4 kilos) with similar fat mass reductions and similar gains in fat-free mass between the two groups. Both groups also improved triglycerides and the triglyceride-to-HDL ratio; it appears that the intermittent fasting group did slightly better in these areas, but the difference was not significant.

The intermittent calorie reduction group did have a significantly greater reduction in insulin levels and corresponding measurements of insulin resistance.

What does this study add to our growing knowledge base?

1. We now have more evidence that intermittent calorie reduction may be equal to chronic calorie restriction for weight and fat mass loss. This finding is important as some patients feel intermittent reduction is more feasible, long-term, than chronic restriction. Also, chronic caloric restriction can lead to an eventual decrease in basal metabolic rate and the risk of weight regain. Intermittent reduction does not appear to create the same concerns.
2. This study demonstrates that participants who were practicing intermittent fasting experienced a gain in fat-free mass. This contrasts with one of the recent studies we covered that suggested time-restricted eating led to a loss of fat-free mass. Since other studies have contradicted this finding, we weren’t convinced.
   
   This current study further shows that intermittent calorie reduction does not lead to a loss of lean tissue when the underlying diet is appropriate. In this study, the subjects ate 20% of their calories from protein, the most essential nutrient for preserving lean body mass. Unfortunately, we don’t know the prior study’s corresponding value as the authors did not report that data.
3. Intermittent calorie reduction may lead to better insulin sensitivity, even with equal weight loss. The science is reasonably consistent that greater weight loss improves insulin sensitivity more. However, is there something unique about intermittent fasting or significant caloric reduction that independently improves insulin sensitivity? In this area, the science is less established, but this study suggests that there may be something uniquely beneficial about intermittent fasting.

My final conclusion? Stay tuned for more! If the past few weeks are any indication, we will likely see a slew of studies involving different versions of intermittent fasting. Since they will all likely have different protocols and conclusions, it may be challenging to make sense of it all. Keep checking back to see if we can help clear up the confusion.

Thanks for reading,
Bret Scher MD FACC

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