Does your attention turn to the fridge as soon as you park yourself on the sofa each evening? As we have shifted away from the three square meals regimen of our grandparents, our evening eating habits often leave a lot to be desired.
Getting the nibbles at eight or nine o’clock means a slice of cheese, a piece of toast, a handful of granola or — worse — is a common default to settle grumbling stomachs before shuffling off to bed. But calories too close to bedtime can be bad for your health. The authors of a new study are just the latest to urge us to reintroduce an old-fashioned overnight fast to protect heart and metabolic health.
Reporting in the American Heart Association’s Arteriosclerosis, Thrombosis, and Vascular Biology journal, the team of scientists from Northwestern University in Chicago suggest that the dietary secret to better heart health isn’t just about eating healthily or eating less but about how your calorie intake aligns with your sleep. Their research on overweight adults who were at risk of cardiometabolic disease, including heart disease and type 2 diabetes, but otherwise healthy found that eating the last meal or snack three hours before bed led to measurable improvements in blood pressure, heart rate and blood-sugar control.
Closing the fridge after dinner could be the simplest step for a healthier metabolism
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None of the participants in the seven-week trial changed what they ate in the evenings, just when they popped the last morsel into their mouths. In practical terms it meant wrapping up dinner or snacks by 7pm or 8pm if their usual bedtime was 10pm or 11pm. Results showed their night-time blood pressure dropped by 3.5 per cent and their heart rate by 5 per cent as a result, shifts that the lead author, Daniela Grimaldi, research associate professor of neurology at Northwestern University Feinberg School of Medicine, says are associated with better cardiovascular health.
“Timing our fasting window to work with the body’s natural wake-sleep rhythms can improve the co-ordination between the heart, metabolism and sleep, all of which work together to protect cardiovascular health,” Grimaldi says. She adds that this “relatively simple change in meal timing” could also boost night-time autonomic balance — how well your autonomic nervous system regulates processes such as breathing and digestion — and your glucose metabolism when you wake up, which helps to ward off type 2 diabetes.
The researchers are not the first to encourage us to close the fridge for good once an evening meal has been consumed. Dr Kate Bermingham, a researcher at King’s College London, warned two years ago that late-night calories are associated with unfavourable blood glucose and lipid levels and those who snacked after 9pm tended to eat sugary, high-fat and more processed foods. Others have suggested a link between late-evening snacking and mental health symptoms such as anxiety. Late eating can interfere with the body’s internal clocks, or circadian rhythms, which help to regulate appetite, hormone release and energy use across the day.
“When food is eaten close to bedtime, the body is generally less well equipped to manage blood sugar and fat metabolism,” says the registered nutritionist Rhiannon Lambert, author of The Fibre Formula. “As digestive processes compete with the body’s natural wind-down period, eating late can also affect digestion and sleep quality, which can both disrupt hormones involved in appetite regulation.”
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Hardcore fasting can be grim and, for many, unsustainable. Last month a Cochrane review of 22 clinical trials involving nearly 2,000 adults found that intermittent fasting, such as fasting every other day or the 5:2 diet of fasting for two days a week, is no better at helping people lose excess weight than standard diets or no structured diet plan at all.
Yet most experts agree that our bodies are designed to fast overnight and that our health will benefit from re-adopting a natural food-free break between dinner and breakfast. “An overnight fast is one of the simplest ways to support long-term health,” says Dr Federica Amati, research associate at Imperial College London’s WHO Collaborating Centre for Health Education and Training, head nutritionist at Zoe and author of Every Body Should Know This. “It isn’t extreme fasting and it isn’t about deprivation. It’s about giving the body the time it expects to rest and reset.”
It is also about reverting to habits that worked for previous generations. Some of us can remember when an evening food curfew was the norm. “Before the rise of late-night snacking and mini meals, most people simply stopped eating after dinner,” says the dietician Bahee Van de Bor, a spokeswoman for the British Dietetic Association. “A regular overnight fast is a way of returning to that pattern.” Here is how and why it works.
What’s the best time to have your last meal?
There isn’t a single “best” time that works for everyone but as the Northwestern team suggested, leaving a gap of about three hours before bed is the best approach.
“A simple, practical rule is to finish your last meal at least three hours before bed, which for many people means eating somewhere between 6.30 and 7.30pm if bedtime is around 10.30 to 11.30pm,” Van de Bor says. “But it is less about rigid timing and more about avoiding large meals or ongoing snacking late at night.”
If you are someone who routinely goes to bed later at midnight or 1am, then the threshold shifts accordingly but you should always avoid nibbles after 9pm. A three-hour gap provides enough time for food to be digested before sleep. “We are generally more metabolically efficient earlier in the day and creating a buffer between dinner and bedtime helps the body shift from digestion into repair and restoration overnight,” says the registered nutritionist Dominique Ludwig, author of No-Nonsense Nutrition.
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And what should you eat last thing?
The optimal evening meal is one that leaves you feeling comfortably full, not stuffed, and allows your body to wind down overnight, rather than working overtime to process food while you are sleeping. Avoid ultra-processed foods and large, high-fat, high-glycaemic index foods — baguettes and wraps, processed cereals — because they can cause blood-sugar fluctuations during the night. “We need to eat enough at lunchtime to carry us comfortably through the afternoon but we also do not want to overload the digestive system late at night,” Ludwig says. “I’d recommend a plate that includes a source of protein, plenty of fibre-rich vegetables, some wholefood carbohydrates and healthy fats with about three tablespoons of wholegrains such as buckwheat, freekeh or quinoa.”
When should you eat breakfast?
Aiming for a 12-hour overnight break from food, aligned with your sleep patterns is a good target. “That is a sustainable way to support metabolic regulation, gut health and potentially long-term brain health,” Amati says. Consistency matters more than trying to eat as early as possible. “Breakfast within one to two hours of waking works well for a lot of people,” Van de Bor says. “But if you are genuinely not hungry first thing, then delaying breakfast can also work, although be careful not to push your eating pattern later into the evening when it becomes more metabolically disadvantageous.”
Do not fall into the trap of delaying breakfast for too long. In midlife, prolonged fasting can sometimes increase stress on the body. “Pushing the first meal too far back often means relying on stress hormones for energy rather than nutrients from our food,” Ludwig says. “Equally, not eating enough at breakfast often leads to energy dips and increased cravings, which can lead to overeating later in the day, so aim for enough calories, protein and fibre at breakfast to stabilise blood sugar, energy and mood for the day.”
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Will it have any effect on weight?
Forward-loading your calorie intake can be helpful for weight loss and maintenance. Nutrition scientists at the University of Aberdeen’s Rowett Institute have shown that eating more of your calories earlier in the day and fewer in the evening curbs overall appetite and helps with weight control.
Delaying your intake can have the opposite effect. American scientists reporting in Cell Metabolism found that eating four hours later than normal changed many of the physiological and molecular mechanisms that favour weight gain.
It is likely that any impact of a regular overnight fast on the waistline will be steady rather than dramatic. “Studies show modest reductions in body weight and body fat, often because appetite hormones become better regulated and late-night, less mindful eating is reduced,” Amati says. “Many people find the approach easier to sustain than strict calorie restriction during the day.”
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It will help to combat damaging inflammation
Metabolically, an overnight fast allows the body to transition from using glucose as its primary fuel to drawing more on stored fat, a process known as metabolic switching.
“This shift improves insulin sensitivity, helps regulate fasting blood glucose and reduces harmful background inflammation in the body,” Amati says. “Importantly, these benefits appear to occur even when calorie intake remains stable, as our studies of over 30,000 people at Zoe Nutrition have demonstrated.”
There are gains for gut health
The gut lining is constantly being repaired and regenerated so that it can control which substances cross from the gut barrier into the bloodstream.
“This repair process is strongly related to our diet, our gut bacteria and our fibre intake — with animal studies indicating that regeneration is supported when the gut is at rest,” Ludwig says.
A break from eating also gives our digestive system time to complete its cycle of breaking down food. “A regular overnight fast supports greater diversity within the gut microbiome,” Amati says. “We know that higher microbial diversity is consistently linked with better metabolic resilience and lower levels of inflammation.”
It might boost brain health
During deep sleep, the brain activates a clearance pathway known as the glymphatic system, which removes metabolic waste. “While direct human data are still developing, we do know that sleep quality and circadian integrity are essential for this process,” Amati says. “Eating in alignment with natural sleep–wake cycles by adopting an overnight fast habit may therefore support these restorative mechanisms.”
