This is how weight is gained

Although people blame vacations, holiday meals and older age, weight is actually gained slowly and steadily over a lifetime. Much like you don‘t notice the slow bodily transformation from teenager to young adult to middle aged, as there’s no clear demarcation, weight stealthily adds up unnoticed – until it is.

More than 40 percent of the adult US population is obese, and since obesity is a risk factor for a multitude of chronic diseases – including stroke, heart disease, diabetes and several cancers – understanding how weight is gained can help mitigate this raging epidemic.

A new study in the Journal of Obesity looks at weight gain over a decade of almost 14,000 statistically representative Americans. The results are concerning.

Over 10 years more than half of the people followed in the study gained 5 percent or more body weight, more than a third gained 10 percent body weight or more, and a fifth added 20 percent.

Weight gain over the decades

The study shows an inverse relationship between age and weight gain. The greatest weight is gained by young people – between 20s and 30s – in which an average of almost 18 pounds of weight is added on.

Between 30s and 40s weight gain averages about 14 pounds. It slows further down to about 10 pounds for the 5th decade of life, and to 5 pounds for the sixth.

This pattern adds up to 47 pounds over four decades.

People usually think that older age and slower metabolism leads to the accurate observational finding that the older the population the greater the obesity incidence. This is not the case according to these findings. 

In fact, people gain the most weight when they’re young, but despite gaining 18 pounds by the mid 30s many young people are not obese – it takes further weight gain to push you into the obese category.

Obesity rises with age because the older you are the more years you have to steadily gain weight, a process that actually starts early on.

Why would weight gain slow down with age? One reason is that the bigger the body, the more energy it needs, so if you gain significant weight in your 20s and 30s, if you continue eating the same amounts you’ll gain less weight in subsequent years. 

Habits over time

We’ll all age with time – it’s inevitable. But we don’t have to get fatter over the decades – that’s avoidable with better eating and exercise habits.

It's mostly eating habits – lifelong habits – that determine weight gain trajectory.

Studies in overfeeding, in which people were fed 1000 excess calories daily for three weeks led to more than 4.5 pounds gained. But the excess weight was lost within 6 weeks after the overfeeding experiment ended. Extend that to 100 days – which is what was done in another study – and weight gain was on average 18 pounds, and although much of the weight was lost when the experiment ended, 3 extra pounds lingered, and the participants continued to gain weight over the years. 

It's what you do day in and day out that matters the most.

It’s wise to take inventory of your eating habits early on (and it's never too late), add highly nutritious healthy foods such as fruits, vegetables and whole grains, and cut out unhealthy, seductive calorie bombs, such as highly processed foods, foods with lots of added sugar, and sugary drinks.

Dr. Ayala