Geschatte leestijd: 4 minutenTaking a break from your diet every two weeks can be beneficial for your weight loss. This is evidenced by recent research from the University of Tasmania.
Continuous dieting and starvation mode
We’ve discussed before how continuous dieting isn’t wise. At least, continuous dieting with a calorie deficit aimed at weight loss (a diet can also be aimed at weight gain, after all).
I particularly see this in people who claim to need a very low calorie intake just to maintain their weight. A lower intake than their weight and body fat percentage would suggest. This calorie count seems to decrease over time, and when they occasionally eat ‘normally,’ their weight shoots up. This confirms the notion that the very low number of calories was indeed necessary.
But this notion is incorrect. Often, these “professional dieters” find themselves in a vicious cycle. They eat less than their body needs for an extended period, causing it to enter a “starvation mode.” The metabolism slows down in an attempt to be more efficient with the available energy. The same low amount of calories suddenly no longer produces the desired results, causing the body to hoard more and burn even less.
The University of Tasmania recently demonstrated this with a randomized controlled trial. They published their findings yesterday in the International Journal for Obesity [1].
Two groups of participants followed a diet in which their current calorie intake was reduced by a third. A drastic reduction indeed. In one group, this diet was continuously maintained for 16 weeks. In the other group, the diet was followed for two weeks, after which a quantity of food was eaten for two weeks, aimed at weight maintenance instead of loss. This cycle was repeated for 30 weeks, so the diet with a calorie deficit was followed for 16 weeks in both groups.
The participants in the group with the alternating diet not only lost more weight than those in the “continuous group,” but they also gained less weight after the study ended. Six months after the diet ended, the participants in the alternating group had lost an average of 8 kilograms more than those in the continuous group.
Professor Nuala Byrne of the University of Tasmania led the research, conducted in collaboration with the Queensland University of Technology and the University of Sydney. She explains that a calorie-restricted diet changes several biological processes in the body, slowing down weight loss and possibly leading to weight gain.
“When we reduce our energy (food) intake during dieting, resting metabolism decreases to a greater extent than expected; a phenomenon termed ‘adaptive thermogenesis’ — making weight loss harder to achieve… This ‘famine reaction,’ a survival mechanism which helped humans to survive as a species when food supply was inconsistent in millennia past, is now contributing to our growing waistlines when the food supply is readily available.”
Professor Nuala Byrne of the University of Tasmania
Diet Break: Take a break, take a Brinta
As mentioned, this was already known. Byrne and colleagues were mainly looking for ways to limit this evolutionary response of the body. These tactics are summarized under the term MATADOR, Minimising Adaptive Thermogenesis And Deactivating Obesity Rebound.
According to Byrne, other popular forms of so-called “intermittent fasting” have not proven to be more successful than continuous dieting.
There is a growing body of research which has shown that diets which use one to seven day periods of complete or partial fasting alternated with ad libitum food intake, are not more effective for weight loss than conventional continuous dieting,” she said.
It seems that the ‘breaks’ from dieting we have used in this study may be critical to the success of this approach.
In May of this year, I wrote an article based on a study that examined the effects of alternate-day fasting. The outcome of that study indeed was that it didn’t provide any additional benefit compared to continuous dieting. However, it might prove easier in terms of motivation to eat 60% of your maintenance needs one day and 100% the next, rather than 80% both days. That will be personal, but it’s nice to have alternatives.
The current study shows that longer periods of dieting followed by a longer break would be more successful. In this case, two weeks. There are still plenty of other options to try out.
However, I would like to add that the results are also highly dependent on the severity of the diet. In this case, participants were only allowed to eat a third of their normal intake. That’s a drastic reduction. To what extent this increases the chance of the ‘starvation mode’ also depends on how much they originally ate. If this was well above their maintenance level, a third of their current intake may not be much below it. The men were obese, averaging 110 kilograms with an average BMI of 34 and indeed were eating too much before. In this case, one-third of their current intake translated to 67% of their maintenance level. From this, you can deduce that they were eating about twice as much as their maintenance needs before participating.
67% is still a significant deficit, which significantly increases the likelihood of the starvation response compared to lower calorie restrictions. For the sake of the study, it’s useful to be able to measure the effect. However, in practice, I wouldn’t quickly recommend someone to go from a large calorie surplus to a large deficit. Mentally, that’s very challenging, and physically, the body will resist it. Personally, I would do this more gradually. In many cases, simply reducing to maintenance level (which already takes into account a potentially higher activity level) may lead to results. When the current surplus is smaller, I might aim for 5 to 10 percent fewer calories than maintenance. This may not get you into your wedding dress in two months, but you also won’t have to remember for the rest of your life the only time you fit into it. Before the pounds came back.
Finally, it’s good to remember that the “diet break” only meant that the participants ate what their bodies needed to maintain weight for two weeks. So, they didn’t go wild and binge on junk food.
References
- N M Byrne, A Sainsbury, N A King, A P Hills, R E Wood. Intermittent energy restriction improves weight loss efficiency in obese men—The MATADOR study. International Journal of Obesity, 2017; DOI: 10.1038/ijo.2017.206
