A lot of pressure is placed on people living with obesity to lose weight. Few people outside the obesity community realize weight loss isn’t the issue. Many people living with obesity have successfully lost weight, weather it’s 20 or 100 pounds, keeping it off is another story. Our body has not evolved to lose weight and actually fights weight loss through a series of physical adaptation.
To start, hormonal changes happen; ghrelin “the hunger hormone” increases. While leptin “the fullness hormone” decreases. This leaves us feeling more hungry and less full every time we eat. Science also shows the adaptation of these hormone levels don’t go back to their baseline after weight has been regained. This is part of the explanation why some people regain all of the weight loss and more after dieting.
We also see muscle efficiency increase, while this sounds great it means our muscle are using less calories to perform the same task. The result is we end up spending less calorie without making any changes to our activity level. This adaptation is usually what people refer to when they say dieting decreases your metabolism.
Even our microbiome influences weight regain. The bacteria colonizing our gut (microbiome), varies from one person to the next. However we see very minimal changes in the different type of bacteria found in one person past the age of 3-5 years old. When we change our diet drastically, we also change the nutrition we provide to our gut. Due to this change, the bacteria in our gut starts to change. This change causes the “old bacteria” to send signals to our brain making us crave the food they want. Keep in mind we have more bacterial cells in our body then human, they have a lot of influence.
This is only a simple explanation of some of the physical adaptation that occur after weight loss. These adaptation happen at different times and at different level of intensity for everyone. Always remember the ability to lose weight and maintain it does not depend on someone’s will power.