Losing weight is always a balancing act.
On the one hand, the faster you lose weight, the more you like what you see in the mirror and on the scale.
What if there were a way to get the best of both worlds, though?
Rapid, sustainable weight loss without the usual side effects?
Well, that’s what scientists at the University of Tasmania wanted to find out in a recent study.
What they found confirmed what many bodybuilders have been doing for years—taking short, planned, highly structured breaks from your diet can make fat loss more efficient and sustainable over the long term.
Let’s see what they did.
The researchers had 51 men follow a diet that provided 67% of their daily energy needs (a 33% deficit, which is fairly aggressive) for a total of 16 weeks.
That worked out to about 2,000 calories per day.
Then, the researchers split the men into two groups:
In short, both groups spent the same amount of time in a deficit (16 weeks), but one would bite the bullet and do it all in one fell swoop, and the other would take two weeks on, two week off.
Here’s what the plan looked like:
As you can see, this means that the group taking diet breaks would take twice as long to reach their goal body weight as the group that stayed in a deficit every day (at least in theory, more on that in a moment).
The researchers provided all of the meals to the subjects throughout the study, which ensured they were actually eating the right amount of calories to lose weight. Everyone was also forced to keep a food diary to stay on track.
One downside of this study is that both groups followed a low-protein diet (only 15 to 20% of calories), which works out to around 75 to 100 grams of protein per day. So, we have to keep that in mind when we look at the results.
It probably didn’t make that much of a difference, though, when we consider that everyone in this study was about 40% body fat, and that people with more body fat can lose weight faster without losing muscle.
After both groups were finished with their weight loss diets, they were allowed to eat how they did before the study.
Then, the researchers checked on them again six months later to see how much of the weight they kept off.
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The group that took diet breaks lost 50% more fat than the group that didn’t.
Here’s what their body weight looked like throughout the study:
The dotted line is the group that dieted continuously, and the solid line is the group that took diet breaks. As you can see, they lost weight consistently faster than the group that continuously restricted calories.
Specifically, the group that took diet breaks lost 31 pounds whereas the group that dieted continuously only lost 18 pounds.
That’s not all, though.
Both groups only lost about 3 pounds of lean mass (some of which was likely glycogen), but the group that took diet breaks also had only half as much of a drop in metabolic rate as the group that didn’t take diet breaks.
You can see what this looks like here:
Now, one thing to keep in mind is that most of the drop in metabolic rate during dieting is simply due to moving around a lighter body. If we look at the number of calories people burned per unit of body weight, the difference looks even greater:
What this means is that by the end of the study, the group that took diet breaks was also burning over 300 more calories per day than the group that dieted continuously.
Most importantly, though, is what the researchers found when they checked on everyone 6 months later.
The group that dieted continuously regained 15 pounds, which meant they were only 7 pounds lighter than when they started the diet. The group that took diet breaks only regained 9 pounds, which meant they had kept off 22 pounds of weight loss when it was all said and done.
Here’s what the weight of both groups looked like over the course of the entire study:
Remember, the dotted line is the group that dieted continuously, and the solid line is the group that took diet breaks.
If you have a lot of weight to lose, you want to schedule some planned diet breaks to maintain your muscle mass and metabolic rate and accelerate fat loss.
The main takeaway was that raising your calories up to maintenance for short periods during your diet can actually help you lose more fat and keep it off.
Now, how you go about this depends on how lean you are and how quickly you want to lose fat.
The biggest problem with taking a two-week diet break every two weeks is obvious: you’re going to be dieting twice as long.
The good news is that you probably don’t need to take diet breaks that often to get the benefits.
Here are some good rules of thumb for implementing diet breaks:
If you have a high body fat percentage that requires you to diet for more than 3 months to reach your goal weight, then you’ll probably want to plan a 1 to 2 week diet break every 6 to 8 weeks.
If you have a low body fat percentage and you’re looking to get even leaner, how you use diet breaks depends on how much fat you want to lose.
If you only need to lose a few pounds, then you could probably suck it up and diet for 6 to 8 weeks to reach your goal.
If you want to get really lean, then you’ll probably want to take a 1-week diet break every 4 to 8 weeks. That should give you most of the benefits of diet breaks without turning your diet break into a never-ending slog.
The bottom line is that if you’re willing to make time for a few diet breaks while you lose fat, you’ll probably wind up leaner, lighter, and happier in the final analysis.
Armistead Legge is the Editor-in-Chief for Muscle for Life and Legion Athletics. He has completed over 100 triathlons and cross-country, cycling, and adventure races, and has researched and written for over a dozen organizations, including the National Institutes of Health. When he isn't helping people get into the best shape of their lives, he's lifting weights, riding his bike, hiking, camping, reading, and making delicious food.