The Best Time to Eat and Why
Work with your body’s rhythms to help minimize two conditions made worse with menopause.
They say timing is everything. When it comes to eating for better health, research suggests that when you eat matters.
I’m not talking about intermittent fasting (IF), which I covered in this post. In IF, you eat all of your food during your chosen, limited-time “window” every day, which is usually 6-8 hours.
In this post, I will talk about the effects of eating at night, particularly too close to bedtime, which most of us do. People living in the U.S. eat 30% or more of their calories at dinner, and about 60% of us also eat well past 9 PM, which may be a set up for poor health.
Total calorie intake probably matters most when it comes to wellbeing. However, research suggests that the timing of food intake relative to sleep may play a role in weight control and type 2 diabetes, two issues that affect women more in midlife.
The Body Keeps the Pace
The body has 24-hour cycles, called circadian rhythms, that ensure you’re in sync with your surroundings. Light and dark exert the greatest influence on circadian rhythms, and the body has “clocks,” that regulate rhythms, including those that work with food intake.
The brain houses the central timekeeper, called the suprachiasmatic nucleus (SCN). The SCN is coordinated with the light and dark produced by the earth’s rotation and it regulates bodily activities, including when you go to sleep and wake up.
As night approaches, the SCN directs the body to make melatonin, a hormone that helps you feel tired. When morning approaches, the SCN tells the body to increase another hormone called cortisol, which helps you wake up and start the day. The SCN is synchronized with other clocks in nearly every tissue and organ in your body. These peripheral clocks regulate thousands of functions, such as making nutrients and other compounds available to cells at the right time.
Everyone has their own “biological evening,” which is the time of day when the body naturally starts to feel sleepy due to increased melatonin production, and their own “biological morning,” which is brought on by increased cortisol production. Though most of us are on a similar sleep/wake cycle, some people are particularly early risers, and some are so-called night owls who like to stay up late.
Disrupting Circadian Rhythms Has Consequences
Humans are designed to feast when the sun is up and to fast when it’s down. But modern life, which includes staying up past your bedtime, eating well after the sun sets, or both, works against the internal clocks that rule your metabolism. Failing to obey your body rhythms can affect your health during perimenopause and beyond by encouraging weight gain, type 2 diabetes, or both.
Declining estrogen levels in perimenopause may play a role in the development of type 2 diabetes, though aging also adds to your chances for the condition. When you eat may also be a risk factor.
A 2015 study published in the Proceedings of the National Academy of Sciences showed that glucose tolerance – the body’s ability to clear glucose out of the blood - is lower in the biological evening than the biological morning, probably because insulin levels are higher earlier in the day.
Insulin is a hormone that helps cells absorb glucose from the bloodstream. Insulin has a circadian rhythm. Insulin levels are higher in the morning and into the afternoon, which means that in most cases the body is better equipped to handle the glucose generated by digestion at breakfast and lunch than at dinner and afterwards.
A 2024 Nutrition & Diabetes study found that the later people ate at night, the higher their levels of hemoglobin A1C, a marker for diabetes risk. And a 2023 study in the European Journal of Nutrition also found that regularly snacking after 9 PM resulted in higher hemoglobin A1C levels.
In addition to insulin’s circadian rhythm, there’s another possible reason why it’s harder to regulate blood glucose when you eat later in the evening. As I mentioned earlier, as the sun goes down, levels of melatonin rise in the body. Melatonin reduces insulin secretion into the bloodstream. That makes sense, since you’re supposed to be getting ready to go to bed, not eat.
Higher levels of insulin in the morning may be why a 2019 International Journal of Obesity study concluded that people consuming more of their daily calories within two hours of waking were less likely to have overweight and obesity. Likewise, those in the study who ate a greater amount of their total daily calories within two hours of going to sleep had a higher chance for overweight or obesity.
Skipping breakfast and eating most of your calories later in the day may encourage the body to store more fat. A 2020 PLOS Biology study of people ages 51 to 63 gave participants two different eating plans for one week in a controlled environment, then had them switch to the other diet. One group began the day at 8 AM by eating a 700-calorie breakfast, and having lunch and dinner only, while the other group ate lunch at noontime, had dinner, and ended their day with a 700-calorie late night snack. The researchers found that the later eaters stored more fat and suggested that older people should avoid snacking after dinner to help prevent fat gain.
How to Eat in Sync with Your Body Clock
As I said earlier, many people eat most of their calories at night, increasing the risk for overweight and type 2 diabetes. To make matters worse, nighttime snacking is more likely to include high-calorie, sugary or highly refined foods such as cookies, candy, and snack chips, which may produce more of a rise in blood glucose than nutritious choices such as plain yogurt, cottage cheese, fruit, or vegetables.
Consuming the majority of your calories at breakfast and lunch could make it easier to control your weight, discourage fat gain, and lower the risk for type 2 diabetes. Try these tips to stay in sync with your body.
Frontload your day. It’s a good idea to eat within two hours of waking up because your body expects food in the morning.
Starting to eat earlier in the day and curbing nighttime eating may reduce hunger that naturally curbs calorie intake throughout the day. When people who participated in a randomized controlled study published in 2022 in Cell Metabolism ate an early breakfast and an early dinner, they reported less hunger than those who ate a late breakfast and a late dinner.
If you’re not hungry for breakfast, you may be eating too many of your calories in the evening.
Eat balanced meals and snacks on a regular basis. Include adequate amounts of protein and fiber in every meal and snack to keep yourself fuller for longer, particularly at dinner. A satisfying dinner helps reduce or eliminate nighttime snacking.
Coordinate eating with sleeping. Adequate sleep is necessary for the proper function of your internal clocks. Experts recommend seven to nine hours of sleep every night. Eating or drinking further from bedtime improves the chances for sleeping for the suggested amount of time and may help prevent you from waking up during the night.
Go to sleep at the same time every night and wake at the same time each morning, even on weekends. If hot flashes or racing thoughts are keeping you up, speak with your doctor about solutions.
Avoid alcohol in the evening. Alcohol is a relaxant, but it can prevent you from getting the deep sleep you need. A 2020 Progress in Neuro-Psychopharmacology and Biological Psychiatry found that alcohol may disrupt the circadian rhythms of melatonin and cortisol, the hormones that help regulate your sleep/wake cycle.
Do your daily habits work with or against your circadian rhythms? Let me know in the comments!
Just like my mom, if I stop eating after supper, I lose, or at least, stop gaining weight. And you have written about the science behind that so well. This article will be shared.
Great information! Thank you for this. I developed gut issues a couple years ago, which I believe were in part due to shifting hormones. What's helped me get my gut health back on track was diversifying the amount of whole foods I'd been eating (which unfortunately meant kicking my longterm vegan diet to the curb), cutting out everything even remotely processed, and IF. I try not to eat until noon every day but I also listen to my body and if I'm hungry at 9 or 10, then I'll eat. Most nights I don't snack after dinner and I try to eat my dinner no later than 6 or 7pm.
So far this method has helped me heal my gut but also maintain a steady weight as I enter perimenopause. But as we all know, the only constant is change and I anticipate I'll be making tweaks to my diet for years to come in order to keep up with changing hormones.