If you are attempting to lose a significant amount of weight, I highly recommend implementing a strategy involving diet breaks.
Dieting for a long period of time can be mentally taxing, but there are also metabolic adaptations that occur. These adaptations result in reduced total daily energy expenditure (TDEE).
This could also be interpreted as having a slower metabolism.
The combination of these two things and other factors can make it difficult to consistently make progress over the long term.
One way around this is a diet break, where you eat at your maintenance calories for a certain period of time. This timeframe is generally 1-2 weeks, but it could be longer.
The MATADOR Study
The first major study that brought diet breaks to my attention was The MATADOR Study. This study involved 2-week breaks that were implemented once a month e.g. diet for 2 weeks, break for 2 weeks.
MATADOR stands for Minimising Adaptive Thermogenesis And Deactivating Obesity Rebound. It’s a bit wordy but sums it up well. It is basically a dietary approach designed to reverse some of the impacts of metabolic adaptation, while also increasing the likelihood of weight-loss maintenance down the line.
This specific dietary strategy involved consuming a 30% calorie deficit during the diet weeks. This was followed by eating at maintenance calories during the break weeks.
It is important to note that the diet break weeks were NOT weeks completely off the diet. They still involved controlled eating and were designed to be at maintenance calories, rather than a calorie surplus.
The conclusion of the authors came to was: “Greater weight and fat loss were achieved with intermittent energy restriction. Interrupting energy restrictionwith energy balance ‘rest periods’ may reduce compensatory metabolic responses and, in turn, improve weight loss efficiency.”
This sounds great, but one downside worth mentioning is the overall time commitment. It obviously added more time to the whole process.
While the diet break group lost more body weight and maintained their total daily energy expenditure at a higher point, both groups spent 16 weeks in a calorie deficit. This means that the diet break group was studied for 30 weeks total, due to having those breaks every 2 weeks.
The ICECAP Trail
In 2021, Jackson Peos and a team of researchers produced a larger diet break study with 61 participants.
The protocol was 12 weeks of continuous dieting vs 4 x 3 week blocks that were broken up with 1 week breaks.
The diet break group took 15 weeks total.
Overall fat loss was similar between both groups. The maintenance of metabolic rate was similar as well.
This adds to the thought process that diet breaks do not have a massive impact on things like reversing metabolic adaption. Although I am of the belief that longer breaks at maintenance likely do have more of an impact.
What Jackson and his team did find though is that the biggest benefit of diet breaks was a reduction in hunger.
The participants in the diet break group experience lower hunger, lower desire to eat and greater satisfaction. This was also backed up by a reduction in peptide YY, which regulates appetite.
The key takeaway that Jackson posted on Instagram was: “These hunger and adherence benefits must be weighed up against the greater time commitment of weight loss when incorporating diet breaks into your regimen.”
Will I Gain Weight During a Diet Break?
In terms of physically gaining a noticeable amount of fat and/or muscle, no you will not. This is because the goal is to be eating at maintenance calories. Maintenance calories are technically the number of calories required to maintain your body weight.
But to just answer the question by saying “no you will not gain weight,” would also be a lie.
During a diet break you WILL likely gain a small amount of weight. But this will almost exclusively be due to glycogen and water weight.
Glycogen is our body’s storage form of carbohydrate. If you have been having a reduced amount of carbohydrates while in a calorie deficit, you likely have less glycogen stored.
By consuming more carbohydrates during a diet break, you will likely store more carbohydrate as glycogen.
Glycogen itself has physical weight, so if you stored 100g of glycogen, that is an extra 100g of body weight.
That’s not a lot by itself, but glycogen also draws water in as well. Typically 1g of glycogen brings in 3-4g of water. So that 100g of glycogen example could actually translate to 500g of body weight due to the addition of water weight.
Beyond that, going from a lower sodium intake to a higher sodium intake also encourages your body to hold onto more water. This will further increase your body weight.
This should not be a massive difference, but if you go from being in a calorie deficit to eating at maintenance calories, your weight will likely increase.
Since the increase in weight is completely unrelated to body fat, it would not be something that you should be stressed about.
Single Day Refeeds and Cheat Meals
The obvious downside of diet breaks is that it extends the total timeframe. In the case of The MATADOR Study, it increased the duration from 16 weeks to 30 weeks, due to having a diet break after every 2 weeks of dieting.
The alternative some people will propose is having a refeed or cheat meal/day once a week.
Back when I first got into the nutrition scene, this was a common strategy. I much preferred the term “refeed” instead of “cheat meal” since it seemed more scientific. A refeed was based on a thought process that involved similar potential benefits to what a diet break can provide.
A lot of the thinking on this topic is based on short term observations though.
For example, some of the adaptations to dieting are regulated by the hormone leptin. As time spent in a calorie deficit progresses, leptin levels typically drop. This contributes to increases in appetite and reductions in TDEE.
A refeed day which is higher in carbohydrates significantly increases leptin in the short term. This was taken by many to mean that it would offset a lot of the negative aspects of dieting such as increased hunger and metabolic adaption.
Unfortunately, these short-term fluctuations in leptin from an individual day are not enough to make a significant difference to longer-term hormone levels and TDEE.
There are other hormones that act similarly in response to a single day refeed as well.
When you look at it from that perspective, that is a day that isn’t really providing noticeable benefits, while also taking you out of a calorie deficit. By taking you out of a calorie deficit without providing any physical benefits, it is likely slowing down your progress.
From another perspective though, one day refeeds can potentially provide psychological benefits that could make the dieting process easier for some.
When comparing a 1-2 week diet-break to a single day refeed/cheat day, the clear advantage goes to diet breaks.
Refeeds Might Still Have Benefits
Up until early 2020, I thought the door was closed on refeeds when it came to most physical benefits. But around that time Bill Campbell et al published a study that was relevant to this discussion. It compared 2-day refeeds each week with a calorie matched group for 7 weeks.
The intermittent energy restriction group ate a 35% deficit during the week and maintenance on the weekend, while the control group ate at a 25% deficit each day. Protein was set at 1.8g/kg/day for both groups.
The intermittent energy restriction group retained more muscle mass. They also preserved their RMR more, which indicates that there could be potential applications for 2-day refeeds.
Potentially a single day is too short but doing two consecutive days can be just long enough to provide benefits.
There is a lack of evidence on this topic beyond this study at this stage though. While it is interesting, I wouldn’t read too much into it just yet.
It is also worth noting that some of these findings have been questioned and some valid points have been raised about whether the differences in fat-free mass and resting metabolic rate actually were significant.
There is an argument to be made that the statistical method used n the study was not appropriate. Another issue is that when you factor in glycogen partially explaining the difference in fat-free mass, since the testing was done only 2 days following the last refeed (compared to a straight deficit for the other group), the difference in fat-free mass is likely much smaller.
Keeping your metabolic rate higher while dieting is always a good goal to strive for. Some form of diet break appears to help achieve this goal.
In practice would I do it the same way as it was done in The Matador Study? Probably not. I would probably do it less frequently since this could be the difference between dieting for 16 weeks and taking 30 weeks to get to a similar result. Most people do not have this kind of patience.
For somebody with a high BMI who is >6 months away from their goal no matter how hard they work, there is no doubt that I would attempt to utilise diet breaks some form. An example that I have used in the past has been one month of maintenance for people who have lost >10kg.
The obvious benefit of this is that it can help with maintaining a higher metabolic rate, but other reasons I use it is because:
1) It helps you mentally since it reduces your feelings of restriction. These feelings are bound to happen if you lose 0.5-1kg a week for >10 weeks.
2) It helps get you into a mindset of what maintaining your weight will feel like when you finally reach your goal. This can be is reassuring. When you change your weight significantly, you will almost always have a fear that you won’t be able to adjust to eating “normally” again.
3) It helps shift your mindset. For example, you might focus more on fueling yourself for your training/exercise habits. Or you could also focus on meeting micronutrient requirements that might have been more difficult to hit in a calorie deficit.
It is difficult to implement this with people who aren’t tracking calories (aka most people attempting to lose weight). That being said, it is still worthwhile to attempt in some way.
There are so many ways to implement a diet break and there is also a lot more research on this topic coming out in the near future, which is exciting!
Currently, my opinion on how to practically implement diet breaks without tracking calories is to modify variables such as increasing meal sizes, adding more carbohydrates, or adding in snacks that were previously excluded because they are slightly higher calorie.
Weight-loss over the long term is hard. This can make it easier. It is definitely worth looking into.
Aidan is a Brisbane based dietitian who prides himself on staying up-to-date with evidence-based approaches to dietetic intervention. He has long been fascinated by all things nutrition, particularly the effects of different dietary approaches on body composition and sports performance. Due to this passion, he has built up an extensive knowledge base and experience in multiple areas of nutrition and is able to help clients with a variety of conditions. One of Aidan’s main strengths is his ability to adapt plans based on the client’s desires. By having such a thorough understanding of optimal nutrition for different situations he is able to develop detailed meal plans and guidance for clients that can contribute to improving the clients overall quality of life and performance. He offers services both in-person and online.