In obese adults, losing weight through bariatric surgery or lifestyle changes both reduce feelings of hunger and loss of control over eating over 12 months. However, for each pound lost, lifestyle...
Mechanism
Synthesis from 1 study
When people lose weight by eating less, their body fights back with stronger hunger signals, so they have to use willpower to eat less — this makes each pound lost feel like a bigger drop in hunger (10.1371/journal.pone.0346240). When people have weight-loss surgery, their gut sends new signals to...
Most probable mechanism
After weight loss, people who lose weight through dieting feel hungrier because their body tries to get back to its old weight, so they learn to fight hunger by thinking hard about what they eat — this makes each pound lost feel like less hunger. People who have surgery feel less hungry because their gut sends different signals to the brain that automatically reduce appetite, without needing to think about it — so they don’t need to use willpower as much. This is why dieting leads to a bigger drop in hunger per pound lost: the brain is working harder to override biology, while surgery changes the biology itself (10.1371/journal.pone.0346240).
Calorie restriction during lifestyle weight loss reduces adipose tissue mass, leading to decreased leptin and increased ghrelin secretion, which activates hypothalamic NPY/AgRP neurons to increase subjective hunger and food motivation (10.1371/journal.pone.0346240)
Persistent hunger signals from low leptin and high ghrelin enhance activity in the mesolimbic dopamine pathway, increasing the salience of food cues and cravings (10.1371/journal.pone.0346240)
Repeated cognitive effort to restrict food intake strengthens prefrontal cortical inhibition over limbic reward responses, leading to increased cognitive restraint as measured by validated eating behavior questionnaires (10.1371/journal.pone.0346240)
Bariatric surgery alters gastrointestinal anatomy, accelerating nutrient delivery to the distal ileum and triggering increased secretion of GLP-1, PYY, and CCK from L-cells (10.1371/journal.pone.0346240)
Elevated GLP-1, PYY, and CCK bind to receptors in the hypothalamus and nucleus tractus solitarius, inhibiting orexigenic neurons and reducing hunger perception without requiring conscious restraint (10.1371/journal.pone.0346240)
Gut hormone changes reduce activity in brain reward regions such as the striatum and orbitofrontal cortex, diminishing the motivational value of high-calorie foods and decreasing cue-driven eating (10.1371/journal.pone.0346240)
Evidence from Studies
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