Why does sleep change during weight loss?

Sleep and weight affect each other in both directions. Broken sleep influences the hormones involved in appetite, and excess weight is a recognised risk factor for obstructive sleep apnoea, which itself breaks sleep. Changing one tends to move the other.

For people with sleep apnoea, weight loss can improve symptoms, though it is not a substitute for the treatment that has been prescribed and any change to that is a clinical decision. For everyone else, appetite and energy through the day are usually the first place a run of bad nights shows up.

Loud snoring, gasping in the night, or daytime sleepiness despite enough hours in bed are worth raising rather than absorbing, because sleep apnoea is diagnosed with a sleep study and left untreated is associated with cardiovascular risk.