Changes in Fat-Free Mass, Protein Intake and Habitual Physical Activity Following Roux-en-Y Gastric Bypass Surgery: A Prospective Study

Abstract

Purpose: Large inter-individual variations in post-bariatric fat-free mass loss (FFML) are observed, which might relate to differences in protein intake and physical activity across patients. We performed repetitive assessments of protein intake and physical activity before and after banded Roux-en-Y gastric bypass surgery, and examined its relations to FFML during 6 months of follow-up.

Materials and methods: FFML (bio-impedance analyses), protein intake (24-h dietary recalls) and moderate-to-vigorous physical activity (MVPA; activPAL) were assessed in 28 patients (4 males, age 42 ± 12 years) before surgery and at 1-, 3- and 6-months post-surgery. Changes in protein intake and MVPA were evaluated with mixed model analysis, whereas associations with FFML were assessed by univariate regression analysis.

Results: Six-month FFML was -7.3 ± 3.6 kg. Protein intake decreased from 80 ± 29 g/day (pre-surgery) to 45 ± 26 g/day (1 month post-surgery (P < 0.001)) and did not improve thereafter (51 ± 21 g/day; P > 0.05). Seven participants (25%) consumed ≥ 60 g protein/day at 6 months post-surgery. Participants performed 7394 ± 2420 steps/day in 54 ± 20 min/day of MVPA, which did not change from pre- to post-surgery (P > 0.05). A higher step count (B = -0.002; 95%CI = [-0.004 - 0.000]; P = 0.048) and higher level of MVPA (B = -0.29; 95%CI = [-0.54 - -0.03]; P = 0.018) were related to a lower FFML.

Conclusion: A lower post-surgery FFML was attributable to higher MVPA levels but not protein intake. This may be due to the low total protein intake and the observation that only a minority of patients achieved a protein intake ≥ 60 g/day. Future studies should focus on interventions to increase post-bariatric protein intake and MVPA levels.

Keywords: Fat-free mass; Physical activity; Protein intake; Roux-en-Y gastric bypass surgery.

Fig. 1

Interindividual variation in fat-free mass loss over time. Each point reflects an individual participant and red lines represents the mean loss at the particular time point. The participant that showed an increase in FFM at T1 and T3 was a male (65 years-old) with a weight loss of 29.9 kg (T6), a high preoperative protein intake (156.7 g/day), a high step count at T0 and T1 (both > 12,000 steps/day), and a relatively high protein intake at T1 (68.5 g/day). FFM = fat-free mass, T1 = 1 month post-surgery, T3 = 3 months post-surgery and T6 = 6 months post-surgery

Fig. 2

Dietary intake of macronutrients over time in grams per day (A) and energy percentage (B) at preoperative measurements (T0), 1 month post-surgery (T1), 3 months post-surgery (T3) and 6 months post-surgery (T6). *P < 0.05

Fig. 3

Protein intake over time in grams per day. Each dot reflects one participant and blue lines represent the mean intake. The dashed line represents the minimal protein recommendation of 60 g/day. T0 = preoperative measurement, T1 = 1 month post-surgery, T3 = 3 months post-surgery and T6 = 6 months post-surgery. *P < 0.05

Fig. 4

Mean and standard error of dietary protein intake from different food categories (A) at pre-surgery (T0; n = 28), 1 month (T1; n = 26), 3 months (T3; n = 26) and 6 months (T6; n = 25) post-surgery. Percentage of participants consuming from the food categories at each timepoint (B)

Fig. 5

Changes in physical activity over time for sitting time (A), step count (B), light physical activity (C) and moderate-to-vigorous physical activity (D). Each dot reflects one participant and red lines represent the group average. T0 = preoperative measurement, T1 = 1 month post-surgery, T3 = 3 months post-surgery and T6 = 6 months post-surgery