Longitudinal Change In Physical Activity And Adiposity In Transition From Adolescence To Adulthood

Abstract

The current recommendations for moderate- and vigorous-intensity physical activity (MVPA) have a poorly-justified, abrupt transition that recommends youth achieve ≥60 minutes/day (min/d) and adults achieve ≥150 minutes/week (≥22 min/d on average). PURPOSE: To examine how body fat mass changes according to changes in MVPA from late adolescence (age 18 years) to early adulthood (age 22 years). METHODS: The study sample included 2,099 participants (1,113 females) from the 1993 Pelotas (Brazil) Study. At ages 18 and 22 years, MVPA was measured using wrist-worn accelerometry and fat mass was measured using dual-energy X-ray absorptiometry. MVPA at age 18 was categorized into two groups: 0-59 and ≥ 60 min/d (no [N] and yes [Y] for meeting the youth recommendation). MVPA at age 22 was categorized into three groups: 0-21, 22-59, and ≥ 60 min/d (N, Y22, and Y60 for meeting the adult or youth recommendation). The combination of these groups created six MVPA groups (N&N, N&Y22, N&Y60, Y&N, Y&Y22, and Y&Y60). Sex-specific multivariable linear regression analyses were conducted to estimate changes in fat mass index (FMI, kg/m2) from age 18 to 22 years according to the six MVPA groups. RESULTS: Among males, compared to Y&Y60 (FMI increase = 1.2 [95% CI = 1.0, 1.4]), Y&Y22 and Y&N had larger FMI increases (1.9 [1.6, 2.1] and 1.9 [1.2, 2.5], respectively). Among females, Y&Y60 and Y&Y22 had an equal FMI increase (1.6 [1.4, 1.9] for both groups), while Y&N had a larger FMI increase (2.4 [1.8, 3.0]). For males and females who were inactive at age 18 years, the FMI increase was the smallest among those with ≥60 min/d of MVPA at age 22 years (0.6 [0.1, 1.1] for males and 1.0 [0.5, 1.5] for females), followed by 22-59 min/d (1.0 [0.6, 1.3] for males and 1.4 [1.1, 1.6] for females), and 0-21 min/d (1.7 [1.1, 2.3] for males and 1.7 [1.4, 2.1] for females). CONCLUSION: These findings suggest that among those who were active in late adolescence, engaging in ≥22 min/d of MVPA in adulthood (adult recommendation) is sufficient to lower fat accumulation for females, but insufficient for males. With respect to healthy adiposity levels, these findings call into question the abrupt change in MVPA recommendations for young adult males.