Objectively-assessed physical activity and weight change in young adults: a randomized controlled trial

Abstract

Background: Reductions in physical activity (PA) are common throughout young adulthood and low PA is associated with weight gain. The SNAP Trial previously reported that two self-regulation approaches to weight gain prevention reduced weight gain over a 2-year period in 18-35 year olds. Presented here are secondary analyses examining changes in PA and the relationship between PA and weight change over 2 years.

Methods: 599 young adults (age: 27.4 ± 4.4 yrs.; BMI: 25.4 ± 2.6 kg/m2) were randomly assigned to 1 of 3 treatment arms: Small Changes (reduce calorie intake by 100 kcals/day & add 2000 steps/day), Large Changes (lose 2.3-4.5 kg initially & increase PA to ≥250 min/wk), or Self-guided (control condition). Small and Large Changes received 10, face-to-face group sessions (months 1-4), and two 4-week refresher courses each subsequent year. Body weight and PA were objectively-measured at baseline, 4 months, 1 and 2 years. Daily steps and bout-related moderate-to-vigorous intensity PA (MVPA: ≥3 METs, ≥10-min bouts) was calculated.

Results: Changes in bout-related MVPA and daily steps did not differ among treatment groups over the 2-year period (p's > 0.16). Collapsed across groups, participants gaining >1 lb. (n = 187; 39.6%) had smaller changes in bout-related MVPA at 4 months, 1 and 2 years relative to those maintaining or losing weight (≤1 lb. weight gain; n = 282, 60.4%, p's < 0.05). Averaged across time points, this difference equated to 47.8 min/week. Those gaining and not gaining >1 lb. did not differ on daily steps (p's > 0.10). Among participants engaging in ≥250 min/wk. of MVPA at 2 years (n = 181), 30% gained >1 lb. from baseline to 2 years, which was not different from those engaging in 150-250 min/wk. (n = 87; 36%; p = 0.40), but this percentage was significantly lower when compared to those engaging in <150 min/wk. (n = 176; 49%; p < 0.001).

Conclusions: On average, PA differences were not observed between young adults assigned to small or large changes self-regulation interventions to prevent weight gain. Regardless of group assignment, higher levels of MVPA were associated with better weight gain prevention over 2 years. Our data suggest that achieving >150 min/week of MVPA is needed for weight gain prevention and that increasing MVPA, rather than steps, should be targeted.

Trial registration: www.clinicaltrials.gov (NCT01183689). Registered Aug 13, 2010.

Keywords: Body weight; Exercise; Physical activity; Weight gain; Young adulthood.

Conflict of interest statement

Ethics approval and consent to participate

Informed consent was obtained from all participants, and procedures were performed in accordance with The Miriam Hospital’s (Providence, RI) and University of North Carolina (Chapel Hill, NC) Institutional Review Boards.

Consent for publication

Not applicable.

Competing interests

Dr. Tate is on the Weight Watchers Scientific Advisory Board and received a research grant from Weight Watchers International. The remaining authors have no conflicts of interest to declare. Further, this study was sponsored by NHLBI and the study sponsor did not have any role in the study design; collection, analysis, and interpretation of data; writing the report; and the decision to submit the report for publication.

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Figures

Fig. 1

a Title: Categorization of participants based upon achievement of ≥250 min/week at 4 months and 2 years. a Legend: ‘Non-adopt’: <250 min/week at 4 months and 2 years; ‘Late adopt’: <250 min/week at 4 months, but ≥250 min/week at 2 years; ‘Maintain’: ≥250 min/week at 4 months and 2 years; ‘Non-maintain’: ≥250 min/week at 4 months but <250 min/week at 2 years. Model adjusts for clinic, gender, race, dietary intake, baseline weight, and baseline PA. b Title: Categorization of participants based upon achievement of ≥2000 steps/day above baseline at 4 months and 2 years. b Legend: Non- adopt: <2000 step increase above baseline at 4 months and 2 years; Late Adopt: <2000 step increase above baseline at 4 months but > = 2000 step increase at 2 years; Maintain: > = 2000 step increase above baseline steps at 4 months and 2 years; Non-maintain: > = 2000 step increase above baseline at 4 months and <2000 step increase above baseline at 2 years. Model adjusts for clinic, gender, race, dietary intake, baseline weight, and baseline steps

Fig. 2

Flow of participants through the study