Effects of high protein intake in obese children

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 less 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.

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 responses
to visually presented food stimuli. The concentration of cortisol in hair is
determined to study a possible relationship between cortisol, stress and
obesity and the metabolic syndrome.

The study has a randomized, crossover, single 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. The study will be conducted in 2 study centers: the
Sophia Children's Hospital-Erasmus MC and the VU university medical center
Amsterdam.

Consumption of a high protein diet (HP) or a normal protein diet (NP). In HP,
children*s (ad libitum) habitual diets will be supplemented with ~13% of energy
from protein per day in order to double daily protein intake. The children will
consume 2 supplements per day (milkshake, dessert, or pancake; the children are
free to choose what they prefer most): 1 in the morning (before breakfast) and
1 in the evening (before dinner). When the children are on the NP diet they
will receive two isoenergetic control supplements containing carbohydrates and
fat but no protein.

Children that participate in the study will consume 2 milkshakes per day for a
period of 8 weeks in total. They will keep a diary and visit the hospital 4
times for a series of measurements that will take about 7 hours in total per
day. The amount of blood samples is minimal using a venous catheter. From March
2014 onwards, there will be no more intravenous infusion of stable isotopes.
The length of the hospital visit will be reduced to approximately 3 hours per
day. The children may benefit from participation in the study by an improvement
in body composition and possible other improvements in for instance markers of
the metabolic syndrome. The risks with participation are negligible. The study
specifically focuses on effects of dietary proteins in obese children as more
clinical and scientific knowledge is needed in this population.