Sleep is the cheapest health upgrade you will ever get

We will spend money on almost anything that promises more energy: coffee, supplements, gadgets, weekend getaways. Yet the most powerful tool for energy, mood and long-term health is free, and most of us treat it as optional.

Adults generally need seven to nine hours of sleep a night. Regularly getting less is linked with weight gain, poorer blood sugar control, weaker immunity, worse mood and slower thinking. Short sleep also makes everything else harder: you crave sugar, skip workouts and snap at people you love.

Start with the clock, not the bed

The single most useful habit is a consistent wake-up time, seven days a week. Your body clock runs on routine. When you get up at the same time every day, falling asleep at night gets easier on its own.

Pick a wake time you can keep on weekends too. Then count back seven and a half to eight hours. That's your target for lights out.

Light is the master switch

Morning light tells your brain the day has started. Ten to twenty minutes outdoors soon after waking, even on a cloudy day, helps set your clock. In the evening, do the opposite: dim the lights in the last hour before bed and keep screens away from your face.

The quiet saboteurs

• Caffeine after lunch. Caffeine stays in your system for hours. A 3 p.m. coffee can still be working at midnight.
• Alcohol as a sleep aid. It may help you drift off, but it breaks up deep sleep later in the night.
• A warm room. Most people sleep better in a cool, dark, quiet bedroom.
• Lying awake in bed. If you can't sleep after about twenty minutes, get up, do something calm in low light and come back when you feel sleepy.

When to get help

Loud snoring, gasping at night or feeling exhausted despite plenty of time in bed can be signs of sleep apnea or another condition worth checking. Long-running insomnia is common and treatable too. A doctor can point you to options, including a structured program called cognitive behavioural therapy for insomnia, which often works better than sleeping pills over time.

Guard your sleep the way you'd guard an important meeting. Very few things you can do for your health pay back so well.