Is being tired making you fat? Sleep’s critical role in weight loss and regulation

When on the journey to getting to a healthy goal weight most people only really think about what exercise they are doing and what their diet is, but the weight loss journey is so much more than that. As well as stress, sleep plays a critical role in weight loss and weight regulation.

When lack of sleep is chronic it makes the weight harder to lose and easier to gain. Just this sentence alone is for many can be a game changer because as many of us may know, proactively trying to lose weight is challenging.

When we are tired we are way more inclined to make a poor food choice, look for a sweet pick-me-up and have bigger portions, plus we find it harder to be compliant to a weight loss journey — it’s just too hard. From a clinical perspective sleep needs to be seen as a core pillar of metabolic health in conjunction with food, exercise and stress management.

There are large observational studies that consistently show adults who sleep less than 6 hours a night have a higher risk of central obesity (belly fat) and overall obesity compared to those who sleep seven to eight hours a night. There was a 2024 meta-analysis of prospective cohort studies that found short sleep duration was associated with an 8 per cent higher risk of abdominal obesity.

Short sleep is also linked with gradual weight gain and with finding it harder to keep lost weight off, suggesting that sleep is not just a marker but an active driver of positive energy balance. These patterns appear across different ages and populations, which strengthens the case for a real biological effect.

When you do not get enough sleep, the hormones controlling appetite change in a way that makes you hungrier and more drawn to highly palatable foods, because ghrelin (which stimulates hunger) tends to rise and leptin (which signals fullness) often falls, together boosting your overall appetite.

There was a controlled trial in healthy men showing sleep restriction increased ghrelin levels and led to a significantly higher calorie intake from snacks, particularly sugary snacks and refined carbohydrates during an ad libitum eating period (where participants are free to eat as little or much as they want) .

Short term sleep deprivation can increase daily energy intake by around 300 to 400 kcal per day, which for some people is a meal which over time leads to weight gain.

Another factor for insufficient sleep is it appears to impair how the body stores fat and manages blood glucose (blood sugar). There are studies indicating that sleep loss can reduce sensitivity to insulin, raise evening cortisol and alter adipokines — signalling molecules produced by adipose tissue that acts like a hormone or cytokine in the body. So all of this means visceral fat accumulation as well metabolic dysfunction.

Plus being sleep deprived is also linked to a lower resting metabolic rate and how weight is lost when calories are restricted, meaning a higher proportion comes from muscle instead of fat, which is the worst way to lose weight. Muscle is a key factor in helping regulate our blood glucose. Think of this over time all of this combined sets the stage for progressive weight gain and belly fat in particular.

Sleep really is a key factor in the weight loss journey and lack of it will blunt the effectiveness of any weight loss program and can do more harm than good with muscle loss and fat.

Sleep needs to be considered in all weight management programs as well as exercise and nutrition. Tracking sleep, routine sleep screening is essential. In tracking sleep good sleep hygiene needs to be implemented as well as awareness of what can damage sleep such as alcohol, caffeine, late night screen exposure and meal timing. Meals should be aligned with circadian rhythms.

Poor sleep does not make you directly overweight but it does create an environment that makes weight gain likely and much harder to lose and maintain weight.

Aim for anywhere between seven to nine hours per night of good quality sleep, this needs to be seen as non-negotiable and a part of the strategy for appetite control, long term weight management and metabolic health.

Sleep really is king, something I tell this to all my patients.