Dr. Sarah Berry: Late dinners harm the intestines, heart, and brain

Dr. Wala’a Hafez: A recent study has shown that abstaining from eating during the hours preceding sleep may help mitigate cognitive decline as we age. The study included 47 women aged between 50 and 79, all of whom were overweight or obese. Researchers asked participants to reduce their daily caloric intake by 500 calories for six months. One group ate within a 12-hour window daily, while the other restricted eating to between 10 a.m. and 6 p.m. Both groups lost an average of about 7 kilograms, but those who stopped eating by 6 p.m. achieved better results in spatial planning and problem-solving tests, with indications of improved memory and learning as well.

According to *The Telegraph*, Dr. Sarah Perry, Professor of Nutritional Sciences at King’s College London and Chief Scientist at Zoe, a company specializing in nutritional data, said: “This study adds to a growing body of evidence that the timing of food intake is as important as the duration of the eating window during the day.”

**Timing of Food Intake**

A study published in the *European Journal of Nutrition* found that eating light meals late at night was associated with negative health outcomes, such as increased body fat and elevated blood sugar levels, even among those who chose healthy snacks. Stopping eating about four hours before bedtime, around 6 p.m., may help the body complete digestion and prepare for sleep, including lowering body temperature and initiating tissue repair and regeneration processes.

Professor Perry explains that our bodies operate on a cycle lasting approximately 24 hours, known as the circadian rhythm or biological clock, which regulates many bodily functions, from gut activity to brain function. Therefore, eating at times that do not align with this biological clock may be one factor that makes late-night eating more harmful to health. Below, Professor Perry outlines the impact of late-night eating on various body organs and offers tips to help minimize its adverse effects.

**How Does Late-Night Eating Affect Your Health?**

**The Brain**

The recent study suggests that having an earlier final meal may help protect the brain from cognitive decline. Professor Perry notes that direct evidence is still limited, but eating late in the evening may negatively affect brain health by disrupting neural signals and influencing sleep, stress hormones, and inflammation levels. Late eating may also reduce deep sleep, the stage during which the brain consolidates memories and clears out waste products that may contribute to cognitive decline. The body needs to lower its temperature to enter this stage, whereas continued digestion and food metabolism may keep body temperature elevated, delaying or reducing the duration of deep sleep. Broad observational studies indicate that late eating is associated with an increased risk of hypertension, type 2 diabetes, and possibly high cholesterol, factors that may raise the risk of vascular dementia.

**The Heart**

Professor Perry states that regularly eating late at night over many years is linked to sleep disturbances, weight gain, metabolic disruption, increased inflammation, and deteriorating blood lipid levels, all of which may increase the risk of heart disease. Studies suggest that triglyceride levels are higher after late-night meals compared to early ones, potentially increasing heart disease risk. Additionally, late eating may prevent blood pressure from dropping to normal levels during sleep, placing extra strain on the heart. Growing studies support this link. In a French study following 103,389 adults, having the last meal after 9 p.m. was associated with a 13% increase in the risk of cardiovascular disease compared to finishing before 8 p.m.

**The Gut**

Research indicates that eating a heavy meal late at night may confuse the gut microbiome—the community of microorganisms living in the digestive tract—and may increase the risk of acid reflux. Professor Perry explains that the gut microbiome, like other parts of the body, operates on a daily rhythm; certain bacteria become active during sleep hours and perform functions that help maintain gut health. Late eating may disrupt this rhythm and affect these functions. The body also prepares for digestion at times when food intake is expected, by secreting digestive enzymes and stomach acid. Eating outside this natural pattern may lead to indigestion.

**The Immune System**

Given the crucial role the gut microbiome plays in supporting and directing immune function, Professor Perry says that late-night eating may disrupt immune responses and promote systemic inflammation in the body. Furthermore, our immune system operates on a strong circadian rhythm, and disrupting this rhythm can lead to chronic, low-grade inflammation. Perry adds: “We know that long-term inflammation forms the basis of many chronic diseases.”

**Weight**

Professor Perry says: “There is evidence suggesting that late-night eating is associated with an increased risk of weight gain and obesity.” She adds: “Interestingly, the same meal, when consumed later in the day, has been shown to stimulate lower levels of satiety hormones compared to when eaten earlier in the day.” This is likely due to differences in how metabolism works throughout the day, disruptions in appetite hormones, and the role of the gut microbiome.

**Important Tips on What and How to Eat**

If you must eat late, especially if you work night shifts, Professor Perry recommends the following:

1. Try to have your main meal at lunchtime and a lighter meal in the evening.

2. Avoid refined carbohydrates and sugary foods that cause sharp spikes in blood sugar levels.

3. A light meal rich in healthy fats, protein, and minimally processed plants is the optimal choice.

4. After eating, take a short walk if possible.

5. Try to maintain a regular diet; consistent eating and sleeping patterns improve our health.

6. Eat dinner slowly to enhance feelings of fullness, especially since satiety signals weaken later in the day.