During weight loss, the body's reduction in energy expenditure in the early phase is related to lower carbohydrate stores and less water inside cells, caused by decreasing insulin and increasing...
Mechanism
Synthesis from 1 study
When you eat less, your body first burns through its sugar stores, which makes water leave your cells and lowers your energy use; later, it switches to burning fat and slows down key organs like your liver and kidneys, making you burn even fewer calories (10.1002/oby.23703). After losing weight,...
Most probable mechanism
When you start eating fewer calories, your body first runs out of stored sugar, which causes water to leave your cells and lowers your energy use; later, your body starts burning fat and slows down the work of key organs like your liver and kidneys, which makes you burn even fewer calories overall (10.1002/oby.23703).
Caloric restriction reduces plasma insulin and increases glucagon secretion, triggering glycogen breakdown and depletion in liver and muscle (10.1002/oby.23703).
Glycogen depletion causes loss of bound intracellular water (3–4 g water per gram of glycogen), reducing tissue volume and metabolic demand (10.1002/oby.23703).
With glycogen stores exhausted, energy substrate utilization shifts to lipid mobilization from adipose tissue (10.1002/oby.23703).
Lipid mobilization is associated with reduced metabolic activity in high-energy organs, including decreased glomerular filtration rate, urea production, heart rate, and core body temperature (10.1002/oby.23703).
Collective reductions in organ-specific metabolic rates and tissue water content drive sustained, mass-independent declines in resting energy expenditure (10.1002/oby.23703).
Less supported by current evidence, but not ruled out
After weight loss, lower levels of leptin and thyroid hormone reduce nervous system activity, making muscles use less energy during everyday movements like walking (10.1002/oby.23703).
Weight loss reduces plasma leptin and triiodothyronine (T3) levels (10.1002/oby.23703).
Low leptin and T3 decrease sympathetic nervous system activity (10.1002/oby.23703).
Reduced sympathetic tone improves skeletal muscle mechanical efficiency during low-intensity activity (10.1002/oby.23703).
Improved muscle efficiency lowers the energy cost of daily physical activity, reducing nonresting energy expenditure (10.1002/oby.23703).
Evidence from Studies
Supporting (0)
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Contradicting (1)
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Changes in body composition and homeostatic control of resting energy expenditure during dietary weight loss
Gold Standard Evidence Needed
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