YOU FEEL CRAP, AND YOU’RE NOT LOSING WEIGHT DESPITE ‘EATING VERY LITTLE’. YOUR METABOLISM ISN’T BROKEN, BUT IT MIGHT NEED FIXING.
The idea of a permanently ‘damaged’ metabolism after periods of dieting in a lower calorie state known as ‘metabolic damage’ has been debunked among the nutrition space.
Acute downregulations of metabolism known as ‘metabolic adaptation’, or ‘ adaptive thermogenesis’ is now widely accepted to be true. It’s widely accepted that basal metabolic rate will return to a healthy, ideal baseline as any dieting induced down regulations or ‘slowing’ of metabolism are only acute in nature.
However, when large durations and great severity of low-calorie availability environments are considered, the idea of RED-S (relative energy deficiency in sport) comes in, and it might be the reason for someone not losing weight despite eating what is perceived as ‘very little.
RED-S refers to the physiological effects of chronically low energy (Calorie) availability, relative to requirements, which includes large reductions in resting metabolic rate and severe health implications . While derived from athletes especially females in sport. I think this situation can have some relevance to society as a whole.
Now, it’s vital we acknowledge that most of the “I eat 1000 Calorie a day, and I’m not losing weight” situation, is almost always down to lack of adherence.
But in instances where severity and duration are so massive, these acute metabolic adaptations can be so severe that the “it’s my metabolism” may hold some truth through the currently unpopular concept of RED-S.
If and when through testing, a large disparity between actual resting metabolic rate and ‘healthy’ metabolic rate is identified. The course of action to solve it, is much the same as correcting normal post dieting adaptive thermogenesis. You need to eat at ideal weight maintenance calories. Going straight up to weight maintenance calories is almost always the way to do it with no need for a slow reverse. But for RED-S levels of severity, slowly reversing under the guidance of a qualified medical professional may hold some utility.
Bottom line; if you feel like crap, you’re showing signs of poor health and struggling to lose weight despite ‘eating so little, I must be in a deficit’. Yep, it’s probably just a lack of adherence, but we shouldn’t immediately throw the concept of a ‘metabolism that needs fixing’ out the window. Although I think confirmation via testings is required before you can use the “it’s my metabolism” card.
 International Olympic Committee (IOC) Consensus Statement on Relative Energy Deficiency in Sport (RED-S): 2018 Update