Everything You Need To Know About Diet Breaks and Refeeds

Luke Tulloch

In this article I'm going to outline what diet breaks are, why we might want to use them, and how to implement them. This is something that is extremely topical at the moment in the fitness industry, but I get a lot of confused questions about it.

I made an accompanying video you can watch below.

There's also audio here:

A diet break is a planned break from being in a calorie deficit. It's usually used to break up a longer dieting period and typically lasts a week or two, but we will get into the specifics of how to implement later.

Why would we want to use a diet break? the answer lies in metabolic adaptation. I've previously written an article about this, so I'll just paste the relevant bits below.

(You can check out those posts here: Part One, Part Two)

Losing weight is a big problem as far as your brain is concerned. As captain of the ship, its job is to make sure you survive long enough to pop out as many kids as you can and that means stocking up on as much fuel as you can hold on to. Can’t make babies if you can’t even get out of the harbour.

Your brain has three main priorities in life: 1. Survive. 2. Sex. 3. Repeat.

Anything that threatens these is met with great hostility, and we’ve had millions of years of evolution to hone this survival instinct.

It takes energy to do stay alive and breed, so we have two strategies to make sure there’s enough around. We can either conserve energy or go out and find more in the form of food. Sitting here in front of our screens in 2019 is thus far the ultimate energy-seeking calorie-sparing machine in human form that natural selection has to offer.

So naturally your brain has a little freak-out when you decide you want abs for Summer. Well, maybe more than just a little freak-out. It has mechanisms in place to sense when the fuel gauge is getting low – your level of bodyfat literally informs the brain via a hormone called leptin how much energy is available to do its two favourite things.

Not only this, but it has a multi-pronged strategy in place for when this happens. Faster depletion of energy reserves means a more drastic response – the harder you push on the accelerator, the more you deplete fuel and the harder your brain steps on the brakes.

To get past the analogies: the more weight you lose, the more your brain fights back by reducing energy output and increasing behaviours associated with energy intake.

How Energy Output Is Reduced

As your metabolism adapts to lower energy availability, we start to see energy output decrease. Weight loss leads to what is called adaptive thermogenesis, which means the number of calories you burn daily starts to go down.

This is partly to be expected. Your metabolic rate is closely tied to body weight, so as you lose weight on a fat-loss diet you’d expect that your metabolic rate would reduce accordingly. We have robust research-validated formulae that can work this out.

The problem is that it happens to a greater degree than we would expect. Let’s say you had two 70kg individuals. One’s been dieting and has lost 5kg so far whilst the other has been weight stable for several months.

Our formula would predict that both have roughly the same resting metabolic rate. However, research has shown that the dieter’s metabolic rate will have adapted to compensate for weight loss and is now lower than we predicted.

How can this be? It’s partly due to greater mitochondrial efficiency, meaning that your mitochondria can get better at deriving energy from the food you eat. We also tend to see a drop in hormones that control metabolism (specifically the thyroid hormone T3). This leads to a decrease in overall energy used at rest and while exercising. Coupled with the reduction in bodyweight and we’re looking at a significant reduction in total daily energy expenditure – perhaps as much as 10-15% below what our predictions say based on bodyweight.

The largest variability in daily energy output between individuals is non-exercise activity (NEAT). NEAT includes mostly subconscious movement like fidgeting, posture and generally how animated you are. It’s impacted to a varying degree between dieting individuals. Some people experience a very large reduction in NEAT and others very little. In fact, there can be up to a 2000 Calorie difference in daily energy expenditure between individuals.

To summarise, as your fuel stores drop your brain begins to step on the brakes in an attempt to preserve what’s left of them.

How Energy Intake Is Increased

Recap: When you lose weight, the fuel gauge goes down. The hormone leptin is the first mate who must go inform Captain Brain. Leptin mediates the reductions in NEAT and energy output, but it also increases hunger hormones. The major player here is called ghrelin alongside its pals insulin and cortisol.

Brain is smart. Brain like food. Brain make you eat.

That’s about the gist of it.

Periodizing the Diet

Most of us think of periodisation as relating to training, but we can also periodize nutrition. Just like we have to change up training, nutrition variables need to be changed at times to elicit the desired response. Sometimes we do this for psychological reasons and sometimes we do this for physiological reasons. Either way, the diet should match evolving goals, rate of weight loss and physical activity levels.

The main variable we might change is the total number of calories coming in. We can also alter the ratios of macro nutrients.

Refeeds

Refeeds involve a day or meal of eating more food. There are multiple ways of doing this including a single high calorie meal, a high calorie day, a specifically high carbohydrate day or just calorie cycling in general throughout the week. The idea is that we want to reset metabolic rate, leptin sensitivity and leptin production but this is highly unlikely to occur to any significant degree in such a short period of time.

A 24 hour refeed bringing calories backup to maintenance does not result in a significant increase in metabolic rate. There is a small increase but nothing of particular note and probably mostly related to the increased cost of digestion due to a larger food intake. This doesn't make it useless - I think that refeed may still hold some psychological and physiological benefit.

For example, the increase in stored glycogen may result in better subsequent training quality in the next few days. It also allows a small psychological break and a goal to focus on throughout the week.

However, there are some potential drawbacks to the 24 hour refeed. For some people, it may result in bingeing. Additionally, Increasing the number of calories on one day a week will negate some of the calorie deficit generated during the past week of dieting which could prolong the necessary diet duration.

For these reasons I don't often use a refeed. Unfortunately both the magnitude and duration of a calorie increase is important to make any noticeable changes to leptin signalling, and 24 hours is not likely to provide much stimulus.

Diet breaks

While there are a few different ways we can slow down metabolic adaptation by manipulating how fast we lose weight, we could also let Brain know we’re doing just fine by eating at maintenance every so often. Remember that leptin is the fuel gauge that tells your brain how much fat is left in storage? It starts kicking and screaming at the brain to do something when we lose body fat and mediates the hormonal changes that contribute to adaptive thermogenesis.

It turns out leptin calms down a bit when we have enough energy coming in. It’s hard to fool though – having a one-off cheat meal or a day at energy maintenance isn’t particularly convincing to Brain that we’re not starving.

Imagine that scenario in our evolutionary history: the brain kicks in multiple mechanisms to help us survive when there’s no food available, we stumble across a half-eaten carcass and gorge ourselves silly for a day – and then what? We’re hardly out of the woods yet; it takes more than one lucky day of eating to prevent death by starvation.

To soothe leptin’s signals to the brain, we probably need a few days of eating at maintenance. I typically recommend at least 1 week at maintenance, and sometimes up to 2 weeks. This seems to be enough time to convince leptin that we’re not going to die hungry.

It also seems that carbohydrate intake has a more powerful effect than other macronutrients, And certainly for exercise performance providing carbohydrate would be the preference.

Importantly, this strategy means that the rate of weight loss over time is slower.

10 weeks of continuous dieting at a 40% deficit will produce more weight loss than 4 weeks of a 40% deficit-> 2 weeks at maintenance -> 4 weeks at 40% deficit. In the latter scenario we’re actually only getting 8 weeks of being in a deficit.

Put it another way: if we have a diet break of 1-2 weeks, it’ll take an extra 1-2 weeks to achieve the same amount of time in a 40% deficit – hence a slower rate of average weight loss.

Mind games

I mentioned earlier that there is a behavioural element to this. So far, we’ve been mostly talking about hormonal changes, and while hormones certainly affect our behaviour, we can’t ignore the psychological element of dieting.

Diet breaks have a role to play here too. Not only can we mitigate hormonal adaptation to weight loss by taking a break every so often, we can also refresh ourselves mentally and reduce social friction. I’ve often pre-empted a diet break around social events like weddings, holidays or birthdays to relieve the pressure of a tough or prolonged diet.

This leads into how to implement diet breaks.

Implementing diet breaks

There are two main ways you can use a diet break. The first is to pre-plan the period at maintenance. This works well in situations when you have an event on and you want to reduce social friction and let your hair down. Preplanning diet breaks can also provide a shorter-term goal to focus on instead of a larger dieting period.

The downside of using this approach is that it is not dynamic enough to consider how you might be feeling at the time. Planning in advance is great, but what happens if you get to your plans diet break and you want to continue dieting? Using a diet break might break momentum and leave you unfocused. what happens when you are dieting and you run into an unanticipated situation where you might need to implement a diet break?

This is where using an unplanned diet break can pay dividends. For example, you may plan to diet for a total of 16 weeks with 2 weeks of maintenance somewhere during that period to use at your discretion.

An experienced dieter can make great use of this as a prophylactic. Recognizing the signs of metabolic downregulation and accumulating fatigue and using a diet break to stop it in its tracks is a useful strategy. The analogy is checking the oil before the engine breaks down.

How to take a diet break – simplified step-by-step

First, decide if you’re going to plan in advance around any specific events like holidays, birthdays etc. or if you’re going to keep it as an ace up your sleeve.

Calculate your maintenance calorie intake based on your bodyweight at the time of taking your break.

Increase your calories to this number, mostly from carbs, and stay there for 1-2 weeks.

• If you find you’re gaining weight every day, you probably over-shot your calories a bit, so just bring them down a touch.

Maintain your training during this time. If you’re doing a lot of training, you might want to bring it down a bit since the focus is on recovery during the diet break.

Go back to dieting once the break is done.

Diet break mistakes

There are a few things that are often done incorrectly with diet breaks.

1. Eating too much during the diet break. You should aim to maintain your weight during a diet break – a little movement up or down is fine since you’ll have shifts in fluid. Reducing diet stress can cause a drop in water retained under the skin, meaning you’ll look leaner and lose some weight. On the other hand, having more carbs available will potentially mean more glycogen storage in muscle tissue, making you look a bit bigger and weigh a bit more.
2. Drastically altering the foods you eat. A great way to achieve a bloated physique and larger laundry loads is to eat a ton of foods you’re not used to having. A better way to go about it is to mostly eat the same, just with larger portions.
3. Using diet breaks too often. It’s normal to feel hungry and more fatigued when you diet. It’s normal and unavoidable that you’ll experience metabolic adaptation when you lose weight. It doesn’t mean you need a diet break every 2 weeks. Now, in some cases this is a viable strategy – there is research such as the MATADOR study that have used 2 weeks on and 2 weeks off for a n extended period of time successfully – but remember that when you’re at maintenance, you’re not going to lose weight. Taking a diet break means you’re extending the length of time it’s going to take to reach your target weight, so it should be used strategically. Often, it’s psychologically easier to just push through and hit your goals sooner rather than prolong the process.

Wrapping up

To summarize, dieting is a stressor and the brain recognises when you don’t have as much energy coming in as usual. Taking a brief period back at maintenance can help stave off hormonal adaptations and relieve psychological stress, but it should be done strategically based on your personal circumstances. There are some potential benefits to shorter refeeds, but accumulated stress from dieting is not likely to be significantly affected unless using a break of at least a week.

Hope this has been helpful!

Please share it around and let me know what you thought.