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Writer's pictureJack Braniff

Why Your Metabolism Slows Down When You Lose Weight & What You Can Do About It


Metabolic Adaptation Nutritionist Birmingham

In theory, reducing food intake enough should result in significant weight loss. However, this is not always the case; more often than not people hit a plateau where they stop losing weight no matter how hard they try. This phenomenon is often due to something called metabolic adaptation – when the body slows down its metabolism in response to caloric restriction. But what is metabolic adaptation, and how can you overcome it to continue losing weight?


Calories in Vs Calories Out is overly simplistic


 The human body is a complex and adaptable system and doesn't always follow the simple "calories in vs calories out" equation.


When you diet, your body starts to adapt in order to conserve energy. This means that it burns fewer calories than it did before, even when you're at rest. This adaptive response is what causes many people to hit a plateau in their weight loss journey – their metabolism has slowed down so much that they can no longer lose any more weight.


The adaptive response is caused by a combination of changes in Resting Metabolic Rate (RMR), Thermic Effect Of Feeding (TEF) and Active Energy Expenditure (AEF). When you eat less, your body burns fewer calories at rest and during physical activity.



Metabolic Adaptation Birmingham
Why metabolic adaptation happens
  1. Resting Metabolic Rate (RMR). Your RMR decreases because you weigh less

  2. Thermic Effect Of Feeding (TEF). Your TEF decreases because you eat less

  3. Active Energy Expenditure (AEF). Your AEF decreases because you move less to conserve energy and weigh less when moving around

  4. Hormonal changes - To make matters worse, hormonal responses (leptin, insulin, testosterone, ghrelin, thyroid) to a calorie deficit also promotes hunger, further reduces the metabolic rate, which makes it difficult to maintain lean mass


The adaptive response makes it harder to lose weight and can lead to weight regain if you don't stick to your diet. This is one of the reasons why "calories in vs calories out" is an oversimplification of weight loss and isn't always an accurate way to predict progress.


How can you prevent metabolic adaptation from happening?


  • Eat enough - A very low-calorie diet can result in RMR being reduced, as well as a reduction in TEF (because you're eating less) and AEF (because you move around less). Eating an adequate amount of calories will prevent RMR from decreasing too much. A simple RMR test can ensure you are eating enough for your weight loss goals and still see results.

  • Take a step approach - Reduce your calories in a step wise by making small incremental changes when you hit a plateau

  • Phase your diet - try and only stay in a calorie deficit for only 8-16 weeks before adding in periods where you increase calories up to maintenance. This can help give you a physical and psychological break from dieting

  • Maintain lean mass - Restricting calories too much can lead to a loss of muscle mass, which will further reduce RMR. By maintaining your lean mass, you'll help offset the decrease in RMR that often comes with dieting. A protein-rich diet and strength training are two great ways to do this.

  • Eat more protein - Protein has a higher thermic effect than carbs or fat, meaning that the body burns more calories to digest it. This can help to offset the decrease in RMR that often accompanies weight loss.

  • Increase physical activity - Increasing your physical activity (weight training and structured cardio) can help to offset the decrease in AEF that comes with dieting.


Final thought


Dieting is hard. We know that. It’s also important to remember that your body is going to fight you every step of the way. That’s why it’s so important to have a good understanding of how dieting and weight loss works before you start – otherwise, you may find yourself struggling unnecessarily.


The adaptive response is something you want to be mindful of when dieting. This means that your body will burn fewer calories, even at rest. To help avoid this, you must make a concerted effort not drastically cut calories and follow some of the steps above to help with your weight loss goals.


Metabolic testing is a process that can help you understand exactly how many calories you need for your goals. Through a simple 15 minute none invasive test we can establish how many calories you are burning at rest and provide you with a nutrition plan based on your unique needs.


For more information about how RMR and fat loss testing and nutrition coaching, check out our Accelerator Programme here https://www.metabolicbirmingham.co.uk/





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