Sleep and weight

The finding that should be better known

In controlled trials where people ate the same deficit but slept different amounts, the short-sleep group lost a substantially larger share of their weight as lean tissue rather than fat. Same diet, same total loss, worse composition. If you are dieting on five hours a night you are partly dieting away your muscle.

Why appetite rises

Short sleep shifts appetite hormones in the unhelpful direction — ghrelin up, leptin down — and the subjective effect is straightforward: you are hungrier, particularly for calorie-dense food, and your capacity to decline it is lower. Sleep restriction studies consistently show people eating a few hundred extra calories a day without intending to, concentrated in evening snacking.

There is also a simple mechanical effect. Being awake longer is more hours available for eating, and the hours in question are the ones where the biscuits live.

Insulin sensitivity

Even a few nights of restricted sleep measurably worsens insulin sensitivity in healthy young adults. That matters generally and it matters more in a population already predisposed to insulin resistance — which, as the Asian-Indian BMI guide explains, describes South Asians. Sleep is not a side issue for Indian metabolic health.

What "enough" means

Most adults need seven to nine hours. A minority genuinely function on less; far more people believe they are in that minority than are. A reasonable self-test: if you wake without an alarm at roughly the same time on a free day, you are getting enough. If you sleep three hours longer every Sunday, you are running a deficit during the week and paying it back.

Practical, in an Indian week

• Fix the wake time first, not the bedtime. A consistent wake time drags the bedtime into place; the reverse rarely works.
• Late dinner is the common culprit. Eating heavily at 10:30 pm and sleeping at 11 leaves digestion competing with sleep onset. Moving dinner even 45 minutes earlier is usually more achievable than moving bedtime.
• Caffeine has a long tail. An evening chai or coffee is still measurably in your system at bedtime for many people.
• Heat matters. In much of India, a room that is a few degrees cooler does more for sleep quality than any supplement.

The honest limits

Sleeping well will not, by itself, cause weight loss. The energy deficit does that. What good sleep does is make the deficit easier to hold and protect the muscle you would otherwise lose while holding it — which is why it belongs in the plan rather than in the "nice to have" column. If you are training hard, it is also when the adaptation to that training actually happens.