Whole body room calorimeters to study appetite control, energy balance and the role of dietary protein

Whole body room calorimeters to study appetite control, energy balance and the role of dietary protein: The increasing prevalence of obesity is a major problem in our modern world, a positive energy balance is one of the most critical underpinnings for this development. Weight gain and obesity are known risk factors for type 2 diabetes and cardiovascular diseases. The most straightforward remedy for obesity is weight loss. Weight loss has been associated with adaptations in energy expenditure. Identifying factors that counteract these adaptations are important for long-term weight loss and weight maintenance. The endocannabinoid system (ECS) has been suggested to play a critical role in the regulation of energy balance and in the pathophysiology of metabolic disorders in humans.

Objectives of study

The Maastricht whole body room calorimeters are used as a controlled setting in a study to assess the effect of a high-protein versus a moderate-protein diet on appetite control, validated markers for cardio metabolic health and vascular function, adaptive thermogenesis, and energy balance. These effects were studied in two groups of people in a post-obese state after an 8-week weight loss. Both groups were given either a high-protein/ moderate carbohydrate (HP/MCHO) diet or a moderate-protein/ high carbohydrate (MP/HCHO) diet. It was hypothesized that changes in energy balance and/or changes in concentrations in the endocannabinoids and related compounds could have an effect on the previously mentioned factors.

Protocol and methods

Each member of the two groups had a 48-hour stay in a metabolic chamber, where energy expenditure and the respiratory quotient were assessed by means of a 24hr VO₂– and VCO₂– measurement. These measured values were calculated to the outcome parameters energy expenditure (EE) and the respiratory quotient (RQ). The room calorimeter is an open-circuit diluted flow calorimeter. This system allows for a continuous flow of fresh air directed through the chamber where all in- and outgoing air is analyzed for O₂− and CO₂− concentrations, while the flow through the system is measured.

The room calorimeter system allows blood sampling during the study through the dedicated blood sampling hatches. The room calorimeters tightly controls the room climate and allow thermoneutral study conditions to minimize effects of thermoregulation on energy expenditure, despite the open circuit system. The room calorimeter system is routinely validated using the methanol burn techniques.

The added value of a room calorimetry installation for this study was:

• 24hr profiles of EE and RQ combined with appetite and satiety markers, and nutrition intake
• optimal participant’s comfort during the study duration
• routinely validated equipment with excellent validity and reproducibility.

References

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