How much sleep do you need, and how does it affect your weight and blood sugar?

How much sleep do adults need?

The American Academy of Sleep Medicine and the Sleep Research Society recommend that adults sleep seven or more hours a night regularly. Needs vary a little between people, but very few adults function at their best on less than seven hours over the long term.

What short sleep does to your metabolism

Regularly sleeping less than seven hours is associated with:

• weight gain and obesity;
• type 2 diabetes;
• high blood pressure and heart disease;
• stroke;
• depression;
• a higher risk of death from any cause.

Some ways sleep loss affects the body:

• Appetite: short sleep shifts hunger hormones, increasing appetite, especially for high-energy foods.
• Blood sugar: even a few nights of poor sleep can reduce how well the body responds to insulin.
• Energy and activity: tiredness makes exercise harder and sitting more likely.
• Stress hormones: poor sleep and stress feed each other.

Is it just quantity?

Quality and timing also matter. Shift work, irregular bedtimes and frequent waking are all linked to poorer metabolic health.

Signs of sleep apnoea

Obstructive sleep apnoea is when the airway repeatedly narrows or closes during sleep. It is common, under-diagnosed, and more likely with excess weight, a larger neck size and older age. Signs include:

• loud, regular snoring;
• pauses in breathing, choking or gasping noticed by a partner;
• waking unrefreshed, or morning headaches;
• feeling very sleepy during the day, including while driving;
• needing to pass urine often at night.

Untreated sleep apnoea is linked to high blood pressure and heart problems. It is treatable, so speak to a doctor if this sounds familiar.

Practical tips for better sleep

• Keep regular times: go to bed and wake up at roughly the same time every day, including weekends.
• Get morning daylight, ideally outdoors.
• Limit caffeine after lunchtime.
• Go easy on alcohol: it may help you fall asleep but disrupts sleep later in the night.
• Wind down: dim lights and put screens away for the last 30 to 60 minutes.
• Make your bedroom cool, dark and quiet. During load-shedding or noisy nights, an eye mask and earplugs can help.
• Be active during the day, but avoid hard exercise right before bed.
• If you can't sleep after about 20 minutes, get up, do something calm in low light, and return when sleepy.

For long-term insomnia, a structured therapy called CBT for insomnia (CBT-I) is recommended as a first-line treatment in many guidelines and is often more effective long-term than sleeping tablets.