Specifically, participants who watched several TV shows each day at age 16 were twice as likely to have metabolic syndrome at age 43 than those who watched one show per week or less at age 16.
When evaluated at age 43, 26.9% of participants had metabolic syndrome, and 55% were overweight and obese. Interestingly, high TV watching was associated with certain outcomes -- central obesity, low HDL cholesterol and hypertension at age 43. Low physical activity levels were associated with some different outcomes -- central obesity and high triglycerides.
This study has merits and limitations. It shows an association between a sedentary lifestyle and metabolic dysfunction later in life. It has a high follow-up rate (88%), and the longitudinal nature of the study is valuable.
The results show an association, not causality between watching TV and having metabolic syndrome. Because it shows an association rather than causality, the evaluation of TV watching should be considered more of a "surrogate marker" that likely involves other contributing factors. In particular, the study did not evaluate participants’ diets. This could be a significant factor and was not addressed in the current study.