The term metabolic adaptation is often thrown around in the dieting circle, but what does it really mean? What does it have to do with weight loss? Is it good or bad and how does it affect our fat loss results? Does it impact weight regain? How do we manage it? Today, we will find out!
What is metabolic adaptation?
Simply explained, metabolic adaptation is basically how much lower your metabolic rate is compared to what would be expected based on your lean body fat mass using the typical equation.
There are quite a few studies to show that when you lose weight your resting energy expenditure and basal metabolic rate will be lowered when compared to somebody who has never lost weight with all other factors being equal.
Now you may ask, why does metabolic adaptation matter to me? We can answer your question by saying that if you are on a meal plan that has you eating in a calorie deficit over an extended period of time and if your goals are to lose weight and reduce overall body fat mass, then metabolic adaptation is definitely something you should be mindful of. Although its effects are often exaggerated, it still does exist and thus an appropriate strategy may be necessary if you plan on being in a calorie deficit for an extended period of time.
Metabolic adaptation and the components of metabolism.
Firstly, we need to look at how the components of metabolism and the effect a calorie deficit can have on them.
BMR – Our body weight is the biggest predictor of BMR. So when we are in a fat loss phase and our body weight decreases, we would expect that the amount of energy we require would also decrease.
NEAT – One of the largest components of metabolism that is influenced by metabolic adaptation is our non exercise activity thermogenesis. The longer we are in a deficit, the more efficient our bodies become with energy. Naturally, over the course of a fat loss phase, we start to fidget less and just do less in general due to the decrease in energy availability.
On top of this. An extended calorie deficit can down regulate other functions that contribute to the amount of energy we burn (such as hormones).
How does it apply to weight loss?
If you take person A who weighs 100kg and around 20% body fat and put them on a calorie restricted diet and they lose weight and manage to get down to 90kg at 10% body fat.
Then you compare person A to person B, who is 90kg at 10% body fat but didn’t have to lose a single gram of weight to get there. Even if both are the same body weight and fat mass, in a controlled environment, you will see that person A (who had to lose weight to get to 90kg, 10% body fat) have a slightly lower TDEE than person B. Simple to understand right?
Is metabolic adaptation bad? How does it affect my fat loss results?
To put this simply.
If we had a 100kg person aiming to lose 0.5kg per week. They would need to be in a calorie deficit of 500 calories per day.
Over time, as their body weight drops. The calories that initially had them losing 0.5kg per week will no longer result in a 0.5kg loss due to a decrease in BMR and potentially NEAT.
To combat this we can recalculate our energy requirements based on our new body weight. However, in some cases, our energy requirements may be lower than what is calculated as metabolic adaptation affects everyone differently.
Is metabolic adaptation the cause for weight regain after a fat loss diet?
Interestingly, there are not many studies out that show the correlation between metabolic adaptation and weight regain after a fat loss phase. However, using the information we know so far, with a reduced basal metabolic rate at the conclusion of an extended calorie restricted diet, the more metabolic adaptation that occurred, the higher the chance they will experience weight regain while increasing calories.
Now we know that what accounts for the decreased rate of fat loss over time and the increased chances of weight regain at the end of a diet phase, how do we manage these negative effects? In fact, there are a couple ways we can do just that!
How to combat fat loss plateaus and weight regain and lower the effects of metabolic adaptation?
Let’s use an example of someone that has lost 5kg after being in a caloric deficit for 10 weeks but has noticed that their rate of weight loss has begun to slow. They decide to go on a period of one to two weeks where they consume their maintenance calories, or as most of us already know at this stage is what is referred to as a “diet break” (shorter periods of the same method are referred to as “refeeds”). Not only will this help to reset the hunger hormones in the body, regular diet breaks have been shown to decrease the amount of metabolic adaptation that occurs over a period of time. .
As a result, implementing diet breaks and re-feeds into an extended period of calorie restricted or fat loss diet, is really beneficial for people who want to minimize the effects of metabolic adaptation and also decreasing the chances of weight regain over time after the diet ends.
What can you take away from all of this?
To put everything into context, metabolic adaptation plays a role in our fat loss results as well as our ability to maintain our goal weight. But at the end of the day, it is a caloric deficit and your day to day behaviors and routines that are the pivotal drivers when it comes to losing weight. And it is maintaining those behaviours that will allow you to lose weight and most importantly, keep it off!
Everyone responds differently, so it is important to have a strategy in place that is best suited to you.