“It would appear that weight loss is accompanied by a state of seemingly permanent depression of energy expenditure, which poses a significant challenge to the maintenance of lowered body weight.”
This was the conclusion of E. Doucet et al, (School of Human Kinetics, Faculty of Health Sciences, University of Ottawa, Canada) in a review article published in Obesity Reviews. This review along with an ever increase body evidence help to explain why losing weight is so difficult and weight regain so common.
What they showed in this review is that when you lose weight, the body adapts in multiple ways to make you regain the weight. Ultimately these lead to lower-than-expected weight loss and to weight regain. The following is essentially what they found.
Weight loss lowers your metabolic rate: When they considered all interventions to lose weight, they found that the resting energy expenditure decreased by about 15 Calories for every 2.2 pounds of weight loss. This decrease is far more than is expected by the amount of weight loss alone. This means that a 44-pound weight loss can cause your metabolism to drop by 300 Calories a day. This is very significant. Based purely on the law of thermodynamics, 300 calories decrease in metabolic rate per day could lead to a 30-pound weight gain in a year.
Weight loss increases appetite: Weight loss leads to an upregulation of appetite leading to increase drive to eat. They showed that for every 2.2 pounds of weight loss, there is an upregulation of the drive to eat by approximately 100 Cal over and above pre-intervention level. This increase appears to last for as long as 1 year after the intervention. This has been attributed to decrease in the hormone leptin. Leptin is made in the fat cell and decreases with weight loss. Leptin is a satiety hormone and we become less satiated with weight loss because of the accompanying decrease in leptin. To further complicate matters, there is an increase in the level of hunger hormone ghrelin. This leads to increase in hunger.
Increase in food reward: Weight loss is accompanied by increase in food reward, palatability, and olfaction. In other words, food tastes and smell better after weight loss than before.
Effect of weight loss on exercise and energy expenditure. A study of 530 women aged 50 to 74, showed that 91% of the participant had less than expected weight loss based on the level of exercise. A separate review found that actual weight loss from exercise was 30% of what was calculated or expected. This is thought to be due to due to energy compensation. In other words, the metabolic rate is slower than expected. The energy compensation may even be greater than the decrease in metabolic rate seen with diet alone.
Treating the root cause of weight loss struggle: It is becoming clear that diets and exercise fail due to hormonal adaptations to weight loss. This has nothing to do with willpower as conventionally believed. Long-term successful treatment of obesity is likely going to depend on being able to counteract these hormonal adaptations. This is why the newer obesity drugs such as Semaglutide have been successful and promising. These are gut hormones that communicate with the brain to both decrease appetite and increase energy expenditure.
If you are still struggling to lose weight despite dieting and exercising, it should be comforting to know that it is not a personal failure. It is the strength of human physiology. You should however take on the responsibility of looking for solutions at work. Treatments that target the root causes of the struggle.
Ife Ojugbeli, MD, MBA.