New research shows late-night snacking increases obesity risk

It’s always been well-known advice for people wanting to lose weight to avoid late-night snacking. No wonder, as a host of research shows the link between late-night eating and increased body weight and a higher risk of obesity [1].

The deal with obesity

Obesity afflicts approximately 42 per cent of the US adult population and contributes significantly to the onset of chronic diseases. This includes cancer, diabetes, and other illnesses.

While popular healthy diet sayings advise against midnight snacking, few studies have thoroughly investigated the coincidental effects of late eating on the three primary elements of weight regulation (and, thus, obesity risk). These are regulating calorie intake, molecular changes in fat tissue and number of calories you burn.

Obesity afflicts approximately 42 per cent of the US adult population and contributes significantly to the onset of chronic diseases, including cancer, diabetes, and other illnesses

The science between late-night snacking and obesity

A new study by Harvard Medical School at Brigham and Women’s Hospital discovered how eating impacts our appetite. They also explored the energy expenditure and molecular pathways in adipose tissue [2].

According to senior author Frank Scheer, an HMS professor of medicine and director of the Medical Chronobiology Program in the Division of Sleep and Circadian Disorders at Brigham and Women’s, they wanted to test the mechanisms that may clarify why late eating increases obesity risk. Prior research showed that late eating is linked to increased obesity risk, body fat, and impaired weight loss success, and they wanted to understand why.

The study wanted to answer why the time of eating food matters when every other detail is kept consistent, according to Nina Vujović, researcher in the Medical Chronobiology Program and first author of the study. Vujović, Scheer and their team analysed 16 patients with a BMI (body mass index) in the overweight or obese range. 

Every participant finished two laboratory protocols: one with a strictly scheduled early meal schedule and another with the same meals. These were each prepared about four hours later in the day.

Participants maintained fixed sleep and wake schedules in the last two to three weeks before beginning the in-laboratory protocols. Three days before going into the lab, they strictly complied with identical meal schedules and diets at home.

In the laboratory, participants regularly recorded their appetite and hunger. They provided frequent small blood samples through the day. They measured their energy expenditure and body temperature as well.

To gauge how eating time affected molecular pathways involved in adipogenesis (how the body stores fat), investigators gathered biopsies of fatty tissue from a subset of participants during laboratory testing. This was done in both early and late eating protocols to compare gene expression levels/patterns between these two eating conditions.

A new study by Harvard Medical School at Brigham and Women's Hospital discovered how eating impacts our appetite, energy expenditure and molecular pathways in adipose tissue

Experiment results on late-snacking and obesity

Results yielded that eating later had evident effects on hunger and the appetite-regulating hormones ghrelin and leptin, which influence our drive to eat. Particularly, leptin levels, which indicate satiety, decreased within the 24 hours in the late eating conditions than early eating conditions.

When participants ate at a later time, they also burned calories at a much slower place and exhibited adipose tissue gene expression toward raised adipogenesis and lowered lipolysis – promoting fat growth. Strikingly, these results convey converging physiological and molecular mechanisms which are basic in the link between late eating and increased obesity risk.

So what does it have to do with time?

Eating late at night causes a “significant difference” to hunger levels, how we burn calories after eating and how we store fat. In future studies, Scheer’s team plans to recruit more women to increase the generalisability of their results to a broader population. While this study cohort included only five female participants, it was set up to control for the menstrual phase, reducing confounding but making recruiting women more challenging.

The study reveals the impact of late versus early eating. Here, the effects were isolated by controlling for confounding variables such as caloric intake, sleep, light exposure and physical activity. Still, in real life, many of these factors may be affected by meal timing.

In more extensive scale studies, where tight control of all these factors is not possible, we must consider how other environmental and behavioural variables alter these biological pathways underlying obesity risk. In the future, the researchers are also interested in better grasping the relationship between mealtime and bedtime effects on energy balance.

What to snack on in the evenings?

It’s easy to say that individuals should try to aim for a balanced diet during daytime, so they are not hungry after dinner.

A diet containing a high amount of refined carbs or extra sugars could trigger an imbalance in someone’s blood sugar. Evidence shows that high glycemic index (GI) foods like white bread, sugar, potatoes and the like, cause blood glucose dysregulation [3].

Blood glucose dysregulation may adversely affect a person’s mood and make them crave for more food. Consuming high GI foods or too much calories before bed could also increase a person’s weight.

Here are healthy foods you could snack on if you get hungry in the evening. However, it is essential to highlight again that late-night snacking may lead to weight gain.

Bananas: these increase melatonin production, which can help someone sleep [4]. A medium banana has around 105 calories and is a good fibre source, vitamins and minerals. In addition, they are fast and easy food that can satisfy a hunger pang before bed.

Eggs: these are another rich source of melatonin [5]. They are also a great protein source, with one egg containing 6.28 grams of it.

Nuts: per the FDA, (Department of Agriculture and the Food and Drug Administration), consuming 1.5 ounces of nuts everyday, included in diet low in cholesterol and saturated fat may reduce the risk of heart disease [6]. Another source indicates that nuts, particularly pistachios, contain the highest melatonin content among plant foods [7].

Unsalted and unflavored nuts are the healthiest. Here are others to try:

  • Almonds
  • Brazil nuts
  • Cashews
  • Hazelnuts
  • Macadamia nuts
  • Pecans
  • Pistachios
  • Walnuts

Though technically a legume, peanuts are a good source of tryptophan. Carbohydrates help the body absorb tryptophan and one snack to try in the evening is a slice of toast with peanut butter.

Oatmeal: melatonin is naturally found in oats. Other cereals, like barley and wheat are also relatively good sources of this substance. They are also a healthy whole food containing vitamins, minerals and fibre. However, if a person wishes to maintain a moderate weight, they should have smaller portions of oats and avoid consuming them habitually before bedtime, as this could lead to weight gain. 

You can also try sprinkling cinnamon on their oatmeal, as it helps balance blood glucose and may help manage cravings, weight, and mood [8].

Tart cherries: according to a small 2019 pilot study, Montmorency tart cherry juice improved sleep time and efficiency in people over 50 years with insomnia [9]. Per the research, the melatonin, procyanidins and tryptophan in tart cherries may be accountable for their sleep-promoting effect. Groceries sell tart or sour cherries, which are usually in frozen form. You could try eating them with natural yoghurt, which also contains tryptophan.

Turkey sandwich: turkey meat is an adequate source of tryptophan. Light turkey meat has higher amounts of the substance compared to darker turkey meat [10]. Also, tryptophan has direct impact on sleep. It converts to serotonin and melatonin, which functions in the pineal gland to induce sleep.

Yoghurt: yoghurt is a fantastic source of calcium. Aside from being vital for bone health, research says calcium may also sustain better sleep [11]. Yoghurt is high in protein, which can help you feel fuller. Specifically, consuming casein protein at night may help reduce hunger the following day. If getting this food as a snack, it’s better to choose plain varieties. You can flavour it with unsweetened fruits such as berries.

Late-night snacking is generally not an issue if people occasionally consume healthy foods. However, regular and excessive late-night snacking on less healthy foods could lead to weight gain, obesity, or exacerbated reflux symptoms.

Consuming regular balanced meals daily, exercising and having a relaxing evening routine may help avoid late-night snacking

[1] https://bit.ly/3VO58sk
[2] https://news.harvard.edu/gazette/story/2022/10/study-looks-at-why-late-night-eating-increases-obesity-risk/
[3] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5852768/
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3691879/
[5] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5409706/
[6] https://bit.ly/3VG1q3I
[7] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5409706/
[8] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4466762/
[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5617749/
[10] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4728667/
[11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4440346/

Photograph: Maksim Sviridov/Shutterstock
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