Pre-natal programming

Factors acting before birth may affect the likelihood of becoming obese.

Over the past decade or so, evidence has grown that the time spent in the womb has lasting effects on health.

Babies who develop to term (i.e. are not premature) but are underweight when born typically suffer more from metabolic disorders in later life – such as diabetes or heart disease.

Usually, the mother's nutrition is considered to be the crucial factor governing birthweight, but other environmental factors could have an influence, such as smoking, infection, season of birth and so on. The mother's metabolism (and hence genetic make-up) could also be important.

Why should birth weight have such a big influence so many years later? The best guess is that a mother's relatively poor nutrition 'programmes' the hormone systems of the developing baby. When the baby is born, it is programmed to take in as much energy as possible – the logic being that if the fetus has not been getting many nutrients while in the womb, the environment must be a tough one, and food will be scarce.

Hormonal programming encourages consumption, leading to rapid 'catch up' growth and increasing the youngster's chance of survival. The downside is that these hormonal changes may not be advantageous in later life – predisposing to many diseases.

In terms of obesity, a low birth weight individual will be driven to feed, but if food is plentiful (as it typically is in the West), he or she will easily overeat.

Pre-natal programming

Further reading