The purpose of the study is to find out if patients with constitutional delay of growth have a mismatch between energy intake and utilization (as measured by doubly labeled water) and to compare the improvement in growth and energy balance between a group of boys treated with growth hormone (GH) alone versus those given GH plus added nutritional supplements for one year.

Two groups of boys 7-10 years old who are very short and below average in weight but otherwise healthy will be studied. One group will be observed initially for 6 months and then receive GH injections every day for the subsequent 12 months. Another group of boys will get a high-calorie drink every day for 6 months, and then receive GH injections plus the supplement every day for the next 12 months. We will compare how well boys grow in height, weight and the changes in body composition. We will compare diet and energy usage using the doubly labeled water technique. A battery of hormonal and nutritional tests will be performed, as well as body composition assessment.

Inclusion Criteria:

• Boys 7-10 years old who are very short and below average in weight but otherwise healthy.
• Delay in skeletal maturation > 1 year.

Exclusion Criteria:

• Growth hormone deficiency
• Chronic illness
• Participation in high endurance athletics