A wide range of beneficial health effects have been ascribed to consumption of chocolate, especially dark chocolate, which is rich in bioactive compounds that exert antioxidant, anti-inflammatory, and cardioprotective properties. Consumption of milk chocolate, however, is widely associated with harmful effects (such as weight gain) due to its high caloric content. Findings from a recent study suggest that milk chocolate exerts differential health effects, depending on the timing of consumption.

A growing body of evidence suggests that the timing of food intake plays important roles in metabolic regulation and circadian rhythmicity. For example, eating a large, carbohydrate-rich meal late in the evening impairs glucose tolerance and insulin secretion, contributing to the risk of developing type 2 diabetes.

The study involved 19 Caucasian postmenopausal females with normal weight or overweight (average age, 52 years; average body mass index, 25). The participants followed their typical dietary pattern for the duration of the study, with three interventions in random order: 100 grams of milk chocolate (roughly the amount in a standard size candy bar – 542 calories) with breakfast for two weeks, within an hour of waking up; 100 grams of milk chocolate for two weeks, within an hour before bedtime; and no chocolate for two weeks. A one-week washout period separated each intervention. They completed questionnaires that assessed their hunger and appetite for sweets at various timepoints throughout the study. The study investigators assessed the participants' anthropometric measures, including body mass index, total body fat, and waist circumference. They also assessed the composition and function of the participants' gut microbiota and measured their blood glucose levels, body temperature, and sleep quality.

The study investigators found that consuming 100 grams of milk chocolate in the morning or evening did not cause the women to gain weight. The women reported that they felt less hunger and less desire to eat sweets. When they ate milk chocolate in the morning, they consumed about 300 fewer calories during the rest of the day; their fat burning increased; their fasting blood glucose and waist circumference decreased; and their sleep quality was impaired. When they ate milk chocolate in the evening, they consumed about 150 fewer calories during the rest of the day; their physical activity, heat dissipation after meals, and carbohydrate metabolism increased; and their sleep quality improved. Both timings of chocolate consumption altered the composition and function of the gut microbiota.

These findings demonstrate that the timing of milk chocolate consumption has varied effects on metabolism, dietary intake, and sleep function, potentially influencing overall health. Learn how food timing influences cancer risk in this clip featuring Dr. Ruth Patterson.

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