Adiposity and its correlates

In previous chapters we have dealt with adverse effects of undernutrition in children. This is a widespread problem of long standing, and in many countries it is one that has been improving in recent years. A more recent problem and one that is clearly getting worse is ‘overnutrition’ – the increased fat storage that results from a higher food intake than is necessary to provide for a child's energy expenditure.

The body of a child can be thought of as comprising different compartments, which may be identified in terms of the tissues involved (for example, bone, muscle, adipose tissue, blood) or in terms of their chemical composition (for example, mineral, protein, fat, water). The two do not correspond exactly. Fats have a wide range of different functions in the body (Pond, 1998). The brain, for example, is about 60% fat, mostly in the form of phospholipids and cholesterol in cell membranes. These are structural lipids. Adipose tissue, which is unique to vertebrates, differs from other fat containing tissues in the body because it has evolved as a specialised store of fat, available to provide energy as required. The fat is stored in the specialised fat storage cells of the body, the adipocytes, which contain storage lipids based on triacylglycerol molecules. It is these storage lipids that we are concerned with here, so measuring adiposity is simple in theory – we dissect out the adipose tissue, extract the storage lipids from it and weigh them.