Timing of Chocolate Consumption Tied to Metabolism, Lack of Weight Gain

By Linda Carroll

June 28, 2021

(Reuters Health) - Consuming milk chocolate first thing in the morning or at the end of the day may not cause weight gain, but the timing could affect, sleep, energy and microbiota, a small study suggests.

In a randomized crossover trial, 19 postmenopausal women with normal BMI consumed 100 grams of milk chocolate every day - either in the morning or at night - for two weeks in each condition, and abstained entirely for another two weeks. Fourteen days of eating chocolate did not increase body weight, regardless of the timing, but timing did have differing effects on the women's energy expenditure, appetite, sleep, and gut microbes, according to the results published in The FASEB Journal.

The study shows that "if we eat chocolate in the morning - in a very narrow time window - and don't eat it the rest of the day, it can perhaps help to maintain body weight," said study coauthor, Dr. Marta Garaulet, visiting scientist in the division of sleep and circadian disorders in the departments of medicine and neurology at Brigham and Women's Hospital in Boston, and a professor at the University of Murcia in Spain.

"Another message is that if you usually go running in the morning or exercise intensely in the morning it can be helpful to have chocolate around the time you go to sleep," Dr. Garaulet said. "If you eat chocolate at night when you get up in the morning you will have more energy."

The key, Dr. Garaulet said, is to make sure you consume the chocolate during a narrow time window, about an hour, and not to eat the treat any other time.

To take a closer look at the effect of eating chocolate on menopausal women, the researchers recruited women whose mean age was 52, mean initial weight was 65.5 kg, and mean body mass index (BMI) was 25.0, with mean body fat 32.7%. Exclusion criteria were: BMI higher than 35 kg/m2; endocrine, renal, hepatic, eating or psychiatric disorders; and using any pharmacologic treatment or fiber supplements.

The women were asked to eat their normal daily diet while also participating in each of three conditions for two weeks, in random order, with a week-long washout period between during which they ate no chocolate at all. Baseline as well as measurements at the start and near the end of each condition were taken for each woman, including anthropometry, dietary intake, sleep parameters, actimetry, calorimetry, fasting glucose, stool samples and questionnaires about feelings of hunger.

In the morning chocolate condition, women would consume 100 g of milk chocolate each day within one hour of waking and alongside breakfast, but not eat chocolate at any other time of day, while in the evening chocolate condition, women ate their 100 g of chocolate within an hour before bedtime, but at no other time. During another two-week condition and during washout periods, they were asked not to eat any chocolate at all. At all times, they could eat anything else they liked.

The researchers determined that chocolate consumption decreased hunger and the desire for other sweets. When the women ate their chocolate in the morning their ad libitum energy intake dropped by 300 kcal/day, compared to baseline, and when they had their chocolate at night, energy intake was reduced by 150 kcal/day. But in neither situation did the that reduction equal the energy contribution of the chocolate (542 kcal/day).

Nighttime consumption resulted in a 6.9% increase in physical activity according to actimetry, a 1.3% increase in heat dissipation after meals, and a 35.3% increase in carbohydrate oxidation. It also led to an increase in short-chain fatty acid production and changes in gut microbiota composition.

Morning chocolate consumption reduced fasting glucose by 4.4%, waist circumference by 1.7% and increased lipid oxidation by 25.6%. Heat maps of wrist temperature and sleep records showed that evening consumption induced more regular timing of sleep episodes with lower variability of sleep onset than morning consumption.

"I'll be honest, I was a little surprised by the lack of weight gain," said Dana Hunnes, senior dietitian at University of California, Los Angeles, Medical Center, adjunct assistant professor at the UCLA Fielding School of Public Health, and author of the forthcoming "Recipe for Survival: What You Can Do to Live a Healthier and More Environmentally Friendly Life."

Along with the benefit of not gaining weight, the volunteers also appeared to have a little more physical activity and their body temperatures increased, said Hunnes, who was not involved in the research. "So, they could be burning more calories when at rest," she added.

Still, Hunnes wondered how people were taking in so many chocolate calories without gaining weight, and what would have happened if the study had gone on longer.

Hunnes said she'd also like to see a similar experiment conducted with dark chocolate, which has been shown to have numerous health benefits.

SOURCE: https://bit.ly/3dxXAWb The FASEB Journal, online June 24, 2021.