This paper from last year has been sitting in my queue for awhile. After finally giving in and reading it, I’m kicking myself for not getting to it sooner. It’s pretty great!
This study used data from the Aerobics Center Longitudinal Study, a big data set generated from folks in Texas starting in the 1980’s. Specifically, just under 12,000 healthy adults (~ 3/4 men) with a BMI < 30 kg/m2 were followed for an average of ~ 6 years to see how many developed obesity, and how this related to their exercise habits. Subjects’ exercise habits were recorded at both their baseline exam and at follow-up. Obesity was defined as any of the following: 1) BMI > 30, 2) Waist circumference > 102 cm (men)/88 cm (women), and/or 3) Percent body fat > 25% (men)/30% (women) as measured by the dunk tank or skin folds.
Across the ~6-year follow up, ~7-8% of the sample developed obesity per BMI or waist measurement, whereas 19% of the sample developed obesity per body fat testing. To me, this corroborates the main problem with BMI or waist circumference used in isolation, they underdiagnose obesity.
Compared to those who didn’t lift weights at all, even 1 lifting session per week reduced the risk of developing obesity by 20-30% depending on measurement technique. There was further reduction with more lifting, e.g. those lifting 4-5x/wk had ~40-50% lower risk of developing obesity compared to not lifting at all. While not a linear relationship, this data suggests the more lifting someone does, the lower their risk of developing obesity (especially as measured by percent body fat), all else being equal.
This study also looked at the risk of developing obesity in individuals who don’t exercise, in contrast to those doing lifting only, cardio only, or both. Compared to meeting neither guideline, the lowest risk was seen in those meeting both lifting and cardio guidelines (duh), followed by the lifting guidelines, and then the cardio guidelines. Compared to cardio only, resistance training seemed to have a 5 to 15% advantage, whereas hitting both guidelines was worth another 5 to 10%.