Body Composition

Dieting for long periods can decrease muscle mass and lower resting metabolic rate.PMID: 10381029

On a basic level, Fat lose (weight) is simple, eat fewer calories than the body, but it's difficult to keep a calorie deficit for a long time. This is especially important for people who are new to the fat loss journey (weight) because they may not be familiar with the difficulties that come with losing fat (weight) in Psychology and Physiology over a long period of time. The difficulty of maintaining a fat-loss diet can often result in people ending their diet and even gaining back the body fat (weight) they had managed to lose.

Initially, people see fast results While losing body fat (weight) but after losing a certain weight, fat loss (weight loss) progress slows down, and sometimes it completely stops. When this happens, we call it, our body is reached to a plateau level. To break this plateau level, one needs to understand certain biological factors. Hence, we need to see this through a scientific lens. In science, this plateau level is known as Metabolic adaptation.

During prolonged calorie restriction, the body's metabolic rate may decrease, making further (weight) fat loss more challenging. Hence, Understanding metabolic adaptation, Metabolic set point (Settling point system), Adaptive thermogenesis is essential for designing effective and sustainable Nutrition, Training, and recovery.

Metabolic adaptation is a natural process. The body's ability to adjust its energy expenditure in response to changes in dietary (calories) intake and body composition is also known as Metabolic Adaptation, refers to Adaptive thermogenesis.
NOTE: Adaptive thermogenesis is one specific aspect of metabolic adaptation that relates to changes in heat production and energy expenditure. Both terms are often used interchangeably in the context of how the body regulates energy balance.

When we lose Body Fat (weight), our metabolism will decrease. This is a natural consequence of dieting regarding protective mechanism.
When we lose Body Fat (weight), we have less body mass to keep alive, maintain, and survive, so our metabolism goes down with the decrease in Body Fat (weight).

When we gain Body Fat (weight), our metabolism increases as we have more body mass to keep alive, maintain and perform.
Body metabolic rate follows body weight. The more Body Fat (weight), the higher the metabolism. The less Body Fat (weight) the lower the metabolism.

Metabolic adaptation is a decrease in body metabolism lower than what is based on our body weight loss.
For example, let’s say I used to weight 187 pounds (85 kgs) & my resting metabolic rate (RMR) was 1,800 calories per day
I lost 22 pounds (10 kgs) and now weigh 165 (75 kgs) and my RMR has decreased to 1,700 calories/day (it decreased 100 calories/day)
This is normal. Remember, RMR follows body weight changes.
When this happens, we say the person has experienced metabolic adaptation.

Additionally, High body fat individuals have a lower Adaptive Thermogenesis than low body fat individuals at the same weight. This is because high body fat individuals have more insulation from the fat, which reduces the need to generate heat to maintain body temperature.PMID: 27739007

In order to avoid hitting plateau level, one needs to keep certain things in check.
1) Try to maintain a calorie deficit while training hard enough to maintain as much muscle mass as possible.
2) Quality and Quantity of Sleep.
3) To maintain as much muscle mass as possible, the exact macronutrient composition (Protein and fat) of the diet is important.
4) How much Endurance Training (cardio) Should be performed or need to skip Endurance Training (cardio) completely.
5) Intensity of Weight Training in terms of Poundage selection, Repetition, Number of Sets, Movement (Exercise) Variations.
6) Recovery Phase.
7) Stress Management (Personal and professional).

Uncoupling proteins, mitochondrial changes, gut micro biome (some store calories more, some don’t) a lot of factors influence things.