“Chubby” becomes “overweight” when a baby's weight gain is out of proportion to his or her growth in height. This means that more calories are being taken in than the little body can process. Just like a child's building blocks, the various causes of infant obesity can stack up to structure an unhealthy life, both physically and emotionally. Contributing causes include:

Heredity. Young ones more at risk often come from a family with a history of obesity or weight issues. Having one obese parent raises a child's chances of adult obesity by 40%; two parents, by 80%. Abnormal eating patterns and/or disorders that afflict either parent can also visit the child and contribute to adult obesity. In some rare cases, a child may be born with a type of hormonal disorder that causes infant obesity.

The Folks. Parents' awareness (or lack thereof) about good nutrition is as much a factor as heredity, as studies of identical twins brought up in different environments have shown. One twin who is brought up in a nutritionally healthy environment can be of healthy weight, while the other in a less health-conscious family can be obese.  And even with the best information at hand, parents – perhaps overanxious or over-zealous - can still inadvertently overfeed their baby. Keep in mind that if the reward for crying and fussing is always a taste-treat, it could prove an early eating lesson in the wrong direction for the child.

Stress. Remarkably, even an infant can sense and react to an environment of emotional stress and domestic upheaval. Of course we don't see babies making a crawl for the Haagen-Dazs in the fridge, but stress can still register with them. If they're already learning that food in the mouth is a primary means of comfort, this could contribute to future emotional eating problems.

Activity. The US fitness craze hasn't gone so far that we expect Courtney Cox-Arquette's new little one to be opening up her own gym franchise next week. Most babies are in constant motion (far too constant for many parents), but some are more content to lie back and be entertained by colorful crib mobiles or other visual stimulation than to crawl, squirm, wriggle, and get into everything they can. The more chubby the baby, the less inclined he or she will be to move around; thus a cycle of inactivity and weight gain can begin in infancy.