Overweight women who perform high-intensity circuit training for 5–12 MET-hours per week can achieve significant fat loss and improved metabolic health, even though this amount of exercise is less...
Mechanism
Synthesis from 1 study
Intense circuit workouts make muscles bigger and more efficient at burning fat, so the body uses more calories even when resting — this happens with just 5–12 hours of exercise per week, as shown in the study with DOI 10.1371/journal.pone.0202390.
Most probable mechanism
When overweight women do short, intense circuit workouts with weights and quick transitions, their muscles grow bigger and their cells become better at burning fat for energy. Bigger muscles use more calories even at rest, and the improved fat-burning machinery inside cells keeps burning fat for hours after exercise. This means they lose fat without needing to exercise as long as people doing slow cardio, as shown in the study with DOI 10.1371/journal.pone.0202390.
Mechanical tension from resistance exercises activates mTOR signaling in skeletal muscle, leading to muscle hypertrophy and increased fat-free mass, as directly measured by strength gains and lean tissue increases.
Increased fat-free mass raises basal metabolic rate by elevating ATP demand for protein synthesis, ion transport, and cellular maintenance, resulting in sustained higher energy expenditure at rest.
High-intensity exercise depletes ATP and accumulates lactate, activating AMPK and triggering PGC-1α-mediated mitochondrial biogenesis, which enhances oxidative capacity and fat oxidation efficiency.
Elevated post-exercise oxygen consumption (EPOC) and sympathetic nervous system activation sustain energy expenditure and lipolysis through catecholamine-driven triglyceride breakdown in adipose tissue.
Evidence from Studies
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