Health Risks of Gaining Weight in Adulthood Similar to Risks of Persistent Childhood Obesity

One of the major concerns around the childhood obesity epidemic is that early onset obesity may be associated with greater health risks when these kids grow into obese adults compared to individuals who only become obese as adults.

This hypothesis was recently tested in a study Markus Juonala (Finland) and colleagues in a study published last month in the New England Journal of Medicine.

The researchers examined data from four prospective cohort studies that measured childhood and adult BMI with a mean length of follow-up was 23 years.

Data were compared between four groups:

Group 1: nonobese kids who grew into nonobese adults(n=4742)
Group 2: obese kids who grew into nonobese adults (n=274)
Group 3: obese kids who grew into obese adults (n=500)
Group 4: nonobese kids who grew into obese adults (n=812)

All analyses were adjusted for age, sex, height, length of follow-up, and their respective cohorts.

The not so good new is that when childhood obesity persists into adulthood (Group 3), the risk is markedly higher than in Group 1 (never obese) – unfortunately, this is what happens to most of obese kids as 82% of them grew into obese adults.

The good news, however, is that there was absolutely no difference in the cardiovascular risk factors (diabetes, hypertension, dyslipidemia, or intima-media thickess) between Group 1 (never obese) and Group 2 (only obese as kids but not as adults) – this suggests that any increased risk associated with being an obese kid can be virtually completely reversed if they manage to grow into nonobese adults.

Unfortunately, the health risks associated with adult-onset obesity (Group 4) were exactly as bad as with childhood-onset obesity. In other words, even if you managed to get through childhood with normal weight – gaining weight as an adult put you at the same risk as if you’d been obese all your life.

These findings certainly provide important nuances to the discussions about where obesity prevention and treatment resources should be focussed.

Obviously, if you can prevent or treat childhood obesity, thereby reducing the number of obese adults, you would substantially lower risk. But this may be easier said than done, as so far, we are not exactly sure that ‘successful’ obesity treatment in childhood actually prevents adult obesity (we certainly hope it does but no one has yet shown this to be the case). In fact, in this study, two out of three obese adults were nonobese as kids!

On the other hand, even if you get through childhood with normal weight only to go on and become an obese adult, you may as well have been obese all your life. This finding suggests that potential benefits of treating adult obesity may not depend on whether or not you were an obese kid or not. Incidentally, we are also not sure that treatment success in adulthood is any different between childhood-onset and adult-onset obesity.

I am also very much intrigued by the finding that growing into a nonobese adult essentially reverses all of the risk (and damage?) that may have incurred from childhood obesity. This is in someway reminiscent of how the risks of tobacco smoking are now known to be largely reversed within a few years of smoking cessation.

So, on the one hand, it looks like it may never be too late (even as an adult) to lose the excess weight (at least if you do have weight-related risk factors – EOSS 1+).

On the other hand, any cardiometabolic benefits of preventing or treating childhood obesity will only be relevant to population health if this actually prevents or reduces the burden of obesity in adulthood – simply ‘delaying’ the onset of obesity into adulthood by focussing most of our efforts on kids (as suggested recently by Canada’s Health Ministers), may have less benefit than some of us may suspect.

I look forward to hopefully lively discussion on this issue.

Edmonton, Alberta

p.s. Registration for the International School on Obesity Research and Management (ISORAM 2012, Lake Louise March 25-30 is now open – click here to register).

Juonala M, Magnussen CG, Berenson GS, Venn A, Burns TL, Sabin MA, Srinivasan SR, Daniels SR, Davis PH, Chen W, Sun C, Cheung M, Viikari JS, Dwyer T, & Raitakari OT (2011). Childhood adiposity, adult adiposity, and cardiovascular risk factors. The New England journal of medicine, 365 (20), 1876-85 PMID: 22087679