How Diet Breaks Can Help You With Your Fat Loss Goals

Study review on utilizing diet breaks to improve fat loss efficiency and fight off weight regain

Study Reviewed: Intermittent energy restriction improves weight loss efficiency in obese men: the MATADOR study

Today I wanted to breakdown a rather popular study from a few years back that is often known as the MATADOR study.

MATADOR is an acronym that stands for Minimizing Adaptive Thermogenesis And Deactivating Obesity Rebound.

Essentially meaning reducing metabolic adaptation and reducing weight regain after a diet. Yet, this was a great acronym that is easy to remember. Kudos to the researchers for that.

This study was really cool and exceptionally done too.

The idea was to have two groups both undergo 16 weeks of being in a 33% calorie deficit from maintenance.

1 group would do it in 16 consecutive weeks. (CON GROUP)

1 group would do it in 30 weeks. With 2 weeks of being in a deficit and 2 weeks of being back at maintenance. (INT GROUP)

From there they wanted to see if there was differences in weight loss, fat loss and metabolic adaptation (meaning how much their metabolic rates dropped with weight loss).

Here was the key though, they 2 week diet breaks were not just "eat whatever you want" weeks. They were still controlled. They were just controlled to eat at caloric maintenance rather than being in a deficit.

Meals were also provided to all subjects over the trial to ensure that the subjects were actually eating the prescribed calorie target.

Energy expenditure was measured during baseline and remeasured every 4 weeks during the trial so that the calorie prescriptions were staying appropriate with any changes from weight loss.

Finally the population of this study were all Males (47 subjects) with an average age of around 39, who were classified as obese according to BMI, weight stable for the last 6 months minimum and were engaging in less than 1 hour of moderate/vigorous physical activity per week.

Results

The results in this study were what made this paper so popular. As this really brought some solid evidence to support the use of diet breaks.

The 2 week on, 2 week off group did better in almost all categories.

As you'll see above, for all participants who completed the 16 week intervention, the diet break group lost an average 10 more lbs than the continuous group (18.7 avg loss, for CON, 29.48 avg loss for INT).

The diet break group lost about 10 more pounds of actual fat mass than the continuous group (15.84 avg loss for CON, 25.74 avg loss for INT)

While both groups had statistically insignificant and just very negligible differences in lean mass lost (2.42 avg loss for CON, 3.96 avg loss for INT). Before you mention that the diet break group lost more lean mass, it's important to remember they also lost a significant more amount of weight, so this is to be expected and doesn't really mean they lost more relative lean mass.

Next you'll see that the diet break group also had less metabolic adaption relative to body mass lost. Since the diet break group lost more body mass, we'd expect more reductions in energy expenditure. Yet, they had less absolute changes (a very insignificant amount), but when adjusted for body mass losses, it was a significant difference.

Showing that the continuous group's metabolic rate reduced by an average of 179kcal per day MORE than what would be expected from their body mass changes while the diet break group's metabolic rate reduced tty an average of 86kcal per day MORE than what would be expected.

Since weight regain is a very serious concern after weight loss, this could be helpful. But let's not get that excited, it's also only 93 kcal difference.

Finally and perhaps the takeaway from this paper, was the results of the 6 month follow up. The diet break group maintained their weight loss a little bit better. Which is crucial because even if they both maintained evenly, the fact being that the diet break group lost significantly more weight AND kept it off at an equal to better rate while ALSO having slightly less reductions in metabolic rate is a big win for the diet break group.

It does go without saying there is an obvious downside of the diet break group though.. it took about double the amount of time. Which can be viewed as a non-trivial issue with taking all these diet breaks.

Takeaways

There is plenty of takeaways from this paper, but I'm going to leave you with the ones that pack the most punch.

-Diet breaks can be a very useful way to structure your diet in order to increase fat loss efficiency and perhaps reduce metabolic adaptation slightly.

-If you're concerned about maintaining your weight loss, I actually highly suggest putting some breaks into your diet.

-Diet breaks also don't have to be scheduled in a 2 week on/2 week off manner. You can simply just put them in for times you know a calorie deficit just ain't feasible (holidays are coming up.. which is a great example)

-If you impose a diet break, it's not a break from your diet. It's simply just eating at maintenance, not eating whatever you want.

-If you have a large goal, I do suggest putting breaks in there somewhere. As there seems to be tangible benefits, but equally as important is the fact that you'll be spending weeks practicing what it's like to be at maintenance. Which can be VERY benefical in my experience.

-Finally, this was on a population who was all male, obese and untrained. So who know's what the difference would be if they were training, if this study was done on females or folks who were leaner. Although, I wouldn't really expect any of those factors to make any of these results much different.

Summary

All in all, this was a great study that brought some great evidence in supporting the use of diet breaks for improving fat loss outcomes and helping fight off weight regain.

If you have a large fat loss goal, I highly suggest you implement them. It can be in a 2 week on/2 week off fashion or even say 4 weeks on, 1 week off. But the takeaway is that they are a potentially beneficial tool you can use.

Notable downsides are that it will take longer to achieve your results and could be issues with stopping and starting from a rhythm perspective. So you may need to figure out a method that works best for you!

Cheers

-Coach Dylan 🍻