1. Compared to men who were never overweight, those overweight at age 7 who returned to a normal body mass index (BMI) by age 13 had no increased risk for developing type 2 diabetes.
2. Men overweight at age 13 who returned to normal weight by adulthood had an increased risk of type 2 diabetes greater than those who were never overweight, but less than men persistently overweight into adulthood.
Evidence Rating Level: 2 (Good)
Study Rundown: Obesity and overweight status has led to a dramatic increase in type 2 diabetes in recent decades. While the correlation between type 2 diabetes and childhood BMI is well established, the role of childhood obesity in the future development of type 2 diabetes in adulthood is less clear. In this retrospective study of a large cohort of Danish men, researchers found that the increased risk for developing type 2 diabetes with childhood overweight status or obesity over did not persist if there was a return to normal weight by puberty. These findings suggest the adverse metabolic impacts of high BMI in childhood are reversible and highlight the importance of treating overweight and obesity in the pediatric population.
Strengths of this work include the large sample size, objective data of height and weight for each subject, and correction for education and socioeconomic status. Limitations include the lack of explanatory factors of weight loss in overweight children, the inability of BMI to determine lean versus fat mass, and the narrow demographic of the study’s participants.
Click to read the study, published in NEJM
Relevant Reading: Childhood obesity and type 2 diabetes mellitus
In-Depth [retrospective cohort study]: The authors of this retrospective study used the Danish Conscription Database and National Patient Register to include patients who had the following data available: BMI measurments at ages 7 and 13, examination date, age, intelligence-test scores, and educational level in early adulthood. Overweight and obesity were defined using the Centers for Disease Control and Prevention age-specific and sex-specific criteria. The authors analyzed the association between overweight and the risk of type 2 diabetes at each age with and without adjustment for intelligence-test score, education, and age at examination.
Of the 62 565 men included in the study, 6710 (10.7%) were diagnosed with type 2 diabetes during follow-up. The prevalence of overweight increased from 5.4% at 7 years of age to 8.2% in early adulthood. Men who were overweight at 7 years of age with return to normal weight by 13 years of age and into adulthood had the same risk for type 2 diabetes development as men who had never been overweight (hazard ratio [HR], 0.96; 95% confidence interval [CI], 0.75 to 1.21). Men who were overweight at 13 years of age or 7 and 13 years had a lower risk of type 2 diabetes than men who were persistently overweight, but had a higher risk than men who had never been overweight (overweight only at 7 and 13 years vs. never overweight: HR, 1.47; 95% CI, 1.10 to 1.98 – persistently overweight vs. never overweight; HR, 4.14; 95% CI, 3.57 to 4.79). The associations between being overweight and the risk of type 2 diabetes was the same in those diagnosed between 30 and 60 years old and those diagnosed after 60 years. Intelligence-test scores and educational levels did not modify these associations (P>0.79).
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