Effecten van een hoge eiwitinname bij kinderen met obesitas.

Rationale:

The increasing prevalence of childhood obesity is a major health problem. In obese adults, high protein diets have shown to increase weight loss and preserve fat-free body mass. The effectiveness of these diets can be attributed to favourable effects on both sides of the energy balance, i.e. high protein diets suppress appetite and thereby reduce energy intake and they increase energy expenditure. It is not clear whether these beneficial effects are also present in children. The exact mechanism via which a high protein diet increases energy expenditure is not known, but may be related to increased protein and amino acid metabolism.



Objective:

To assess the effects of a 4-week high protein diet on body composition in obese children. Secondary outcomes are whole-body protein turnover, gluconeogenesis, energy expenditure, markers of the metabolic syndrome, appetite sensations, concentrations of (an)orexigenic hormones, and fMRI responses to visually presented food stimuli.



Study design:

The study has a randomized, crossover, double blind design with 2 intervention periods of 4 weeks separated by a wash-out period of 2 weeks. On day 0 and 28 of both intervention periods the children come to the university hospital for a series of measurements.



Study population:

Obese, pre-pubertal children (age 8-12 years) with a Body Mass Index standard deviation score (BMI-SDS) > 2.3 who are on the waiting list of the ‘Dikke Vrienden Club’ (DVC), a cognitive behavioral therapy program for obese children. Exclusion criteria are obesity that is caused by a somatic treatable disorder and use of systemic steroids.
Intervention: Consumption of a high protein diet (HP) or a normal protein diet (NP).



Main study parameters/endpoints:

The change in body composition (body fat%, fat-free mass, fat mass, fat-free mass index, fat mass index , waist and hip circumference, waist:hip ratio) in obese children who consumed a high protein diet for 4 weeks. Secondary endpoints are whole body protein turnover, gluconeogenesis, energy expenditure, insulin sensitivity, and markers of dyslipidemia and oxidative stress.

In obese children who consume a relatively high protein diet for 4 weeks, the combination of reduced energy intake resulting from an increased satiety and increased energy expenditure together with sparing of fat-free mass induces weight loss which results in a 'healthier' body composition, i.e. a lower body fat% and a higher fat-free mass index.

Measurements at day 0 and day 28 of both intervention periods (4 'testdays'). Some additional measurements outside testdays, like a questionnaire concerning appetite and a food diary.

Consumption of a high protein diet (HP) or a normal protein diet (NP). The children will consume 2 supplements per day. The study has a randomized, crossover, double blind design with 2 intervention periods of 4 weeks separated by a wash-out period of 2 weeks.



HP: Protein, NP: Carbohydrates & fat, protein-free.



The high protein diet strives to dubble the proteinintake to a energy percentage of 25. The children will be given a proteinpowder two times a day which is processed in a milkshake, a pancake or yoghurt. One is taken just before breakfast and one just before dinner. The control group receives also 2 supplements a day, consisting of an iso-energetic control powder with carbs and fat but no protein. This powder is also given through a milkshake, pancake or yoghurt.