What one meal a day does to the day's rhythm
OMAD compresses all daily eating into a single meal, which creates a fast of roughly 22 to 23 hours and an eating window of one to two hours. Across the long fasted stretch insulin settles toward baseline and the body relies more on stored fat for fuel. Catecholamines such as noradrenaline tend to rise during fasting, which supports energy and alertness and is part of why some people report feeling sharp while fasted.
Because nearly all calories arrive at once, the single meal must be large and nutritionally complete to meet daily protein, micronutrient, and energy needs.
Tradeoffs of the single-meal approach
OMAD makes calorie restriction simple for some people by removing most eating decisions, but it can make hitting protein and micronutrient targets harder, may cause a large glucose response to one big meal, and is socially restrictive. Evidence on long-term outcomes is limited, and benefits largely track the calorie deficit it tends to produce.
This is general educational information, not medical advice. OMAD is not appropriate for people who are pregnant, underweight, taking glucose-lowering medication, or prone to disordered eating, who should consult a qualified professional.