Postprandial Metabolic Responses to Sustainable and Non-Sustainable Meals in Healthy Young Men

THERMOS-LUNCH: Effects of Meals Differing in Nutritional Quality and Environmental Footprint on Postprandial Metabolism, Diet-Induced Thermogenesis, Respiratory Quotient, Satiety, and Hydration Status in Healthy Young Men

This randomized crossover study evaluated the acute postprandial metabolic and hydration responses to two standardized lunch meals differing in nutritional quality and environmental footprint in healthy young men. Each participant consumed both meals in separate experimental visits according to a randomized sequence. Postprandial oxygen consumption, carbon dioxide production, respiratory quotient, energy expenditure, diet-induced thermogenesis, substrate oxidation, satiety, and hydration-related outcomes were assessed.

The THERMOS-LUNCH study (Thermogenesis, Hydration, Environmental Impact, Respiratory Quotient, Meals, Substrate Oxidation and Sustainability after Lunch in University Students: a Nutritional Crossover Study in Healthy Subjects) was a randomised, two-period, two-sequence crossover intervention study conducted in healthy male university students. The study compared two standardised lunch meals that differed in nutritional quality and estimated environmental impact: a healthy and sustainable meal and a less healthy and non-sustainable comparison meal. Participants were randomly assigned to one of two intervention sequences: the healthy and sustainable meal followed by the comparison meal, or the comparison meal followed by the healthy and sustainable meal. The two experimental visits were separated by a 7-day washout period.

During each experimental visit, postprandial metabolic responses were assessed using portable indirect calorimetry. Oxygen consumption, carbon dioxide production, respiratory exchange ratio, energy expenditure, diet-induced thermogenesis and substrate oxidation were measured during the fasting baseline period and over the 4-hour postprandial period. Subjective appetite and satiety sensations were assessed repeatedly using 100-millimetre visual analogue scales. Hydration-related measures included total fluid intake, urine volume, urine colour and urine specific gravity measured using a digital refractometer. Total urinary nitrogen, obtained from the 24-hour urine collection, was used to account for protein metabolism in substrate-oxidation calculations, while urinary creatinine was used as a quality-control marker for the plausibility and completeness of the 24-hour urine collection.

Inclusion Criteria:

• Male participants aged 18 to 30 years.
• Students enrolled at the University of Parma.
• Residence or domicile in areas surrounding the University of Parma campus.
• Stable body weight during the previous 6 months, defined as body weight change within ±5%.
• Good general health.
• Willingness to comply with study procedures.
• Written informed consent provided before participation.

Exclusion Criteria:

• Female sex.
• Age younger than 18 years or older than 30 years.
• Smoking.
• Food allergies or food intolerances incompatible with the test meals.
• Chronic noncommunicable food-related diseases, including metabolic, endocrine, or chronic disorders.
• Residence or domicile outside areas adjacent to the University of Parma campus.
• Students enrolled at the University of Parma in Gastronomic Sciences or Human Nutrition Sciences.