Ethnic differences in body composition and substrate utilization: the effect of physical activity and diet.

For the same BMI, age and gender Asians tends to have a higher percentage of
body fat and a lower absolute fat-free mass compared to Caucasians. Lower
fat-free mass was associated with lower energy expenditure at rest. Therefore
the difference in body composition may affect substrate utilisation for energy
metabolism and may result in a chronic imbalance between energy storage and
oxidation, primarily as fat. With increasing body fat percentage, Asians were
also reported to accumulate more fat in the abdominal region and to develop a
higher ectopic fat depot in the liver or intramyocellular compared to
Caucasians. The unfavourable body composition and fat distribution in Asians
may predispose to the development of insulin resistance in a lesser degree of
obesity. The interaction between this genetic predisposition and environment
(dietary pattern and sedentary life style) may increase the risk of developing
the metabolic syndrome.

The aims of this study are:
1. To investigate the difference in body composition, fat distribution, energy
expenditure, substrate and dietary fat oxidation in Asians and Caucasians.
2. To investigate the effect of overfeeding a high fat diet on liver fat and
intramyocelullar lipid content as well as glucose tolerance in Asians and
Caucasians
3. To investigate the effect of a sedentary life-style on the expression of
genes involved in adipogenesis, lipogenesis and lipolysis as well as glucose
tolerance in Asians and Caucasians.

The study will be a comparative study between Asians and Caucasians with a
cross-sectional part and an intervention part (see below).

cross-sectional
Subjects will stay in the respiration chamber for two nights, one day (35 hrs)
to assess energy expenditure and substrate utilization. Before staying in the
respiration chamber, daily physical activity will be measured for 7 days,
followed by 3 days of an energy balance diet. Dietary fat oxidation will be
measured using labelled palmitic acids. Subjects will undergo complete
anthropometric measurement including waist and hip circumference and skinfold
thickness. Body composition will be measured, using underwater weighing to
determine body density and the deuterium dilution technique to measure total
body water.

The results from the cross-sectional part will be used for the intervention.
For each intervention, ten Asian and 10 Caucasian subjects, matched for body
fat percentage will be selected. Hence, there will be 10 Asian and 10
Caucasian subjects in each intervention.
Intervention 1 tests the effect of 3 day overfeeding a high fat-diet containing
60% energy from fat (25% from carbohydrate and 15% protein) on ectopic fat
stores (liver and intramyocellullar) and glucose tolerance. Intervention 2
tests the effect of decreased physical activity, due to staying in a
respiration chamber for 3 days, while receiving a normal energy intake based on
energy needs in daily life, on fat cell gene expression and glucose tolerance.

The risks are minimal, and the (time) burden is reasonable. This research is
not harmful for general health. The fitness test may cause fatigue in the legs
and requires maximal exertion. Taking blood and the fat biopsy may cause a
small bruise at the location where the blood/biopsy is taken. The burden is
proportional to the benefits of the research. The subject receives accurate
information about the personal physical activity level, physical fitness,
energy metabolism, body composition, fat distribution and blood lipid profile.