Changes in total energy intake and macronutrient composition after bariatric surgery predict long-term weight outcome: findings from the Swedish Obese Subjects (SOS) study

Abstract

Background: Approximately 20-30% of obese patients do not achieve successful weight outcomes after bariatric surgery.Objective: We examined whether short-term changes (≤0.5 y postsurgery) in energy intake and macronutrient composition after bariatric surgery could predict 10-y weight change.Design: Participants were recruited from the Swedish Obese Subjects (SOS) study, which was a matched (nonrandomized) prospective trial that compared bariatric surgery with usual care for obese patients. A total of 2010 patients who underwent bariatric surgery were included in the study. Physical examinations (e.g., weight) and questionnaires (e.g., dietary questionnaire) were completed before and 0.5, 1, 2, 3, 4, 6, 8, and 10 y after surgery. For the main analytic strategy, a linear mixed model was implemented, which included repeated measures with a random intercept and an unstructured covariance matrix.Results: Short-term changes in energy intake (P < 0.001) and in relative proportions of energy from carbohydrates (P < 0.001), fat (P < 0.001), and protein (P < 0.05) were associated with 10-y weight change after bariatric surgery. At the 10-y follow-up, men and women with the largest reductions in energy intake had lost 7.3% and 3.9% more weight, respectively, compared with that of subjects with the smallest intake reductions (P < 0.001). Greater weight loss was achieved in men and women who favored protein and carbohydrates over fat and in subjects who favored protein over carbohydrates than in individuals who favored the opposite changes in macronutrient composition (P < 0.05).Conclusions: The level of energy restriction that is achieved at 0.5 y after bariatric surgery predicts long-term weight loss. Weight loss is also associated with a changing dietary macronutrient composition. This trial was registered at clinicaltrials.gov as NCT01479452.

Keywords: Swedish Obese Subjects study; bariatric surgery; energy intake; macronutrients; weight loss.

© 2017 American Society for Nutrition.

Figures

FIGURE 1

Mean (95% CI) relative weight loss after bariatric surgery grouped according to short-term changes (≤0.5 y postsurgery) in energy and macronutrient intakes in men (n = 480). Subgroups were divided according to changes in energy intake and macronutrient composition from baseline to the 0.5-y follow-up. For example, mean intake of carbohydrates was calculated for each time point, and participants were grouped according to tertiles of 0.5-y changes in carbohydrate intake. Similarly, mean intake of fat was calculated for each time point, and participants were grouped according to tertiles of 0.5-y changes in fat intake. Group 3 always represented the largest negative change (i.e., intake reduction; squares with dashed line). Group 1 represents either individuals with the smallest negative change (percentage of energy) or those with the largest positive change (i.e., intake increase; circles with solid lines). Group 2 represents participants with either positive or negative intermediate changes (triangles with solid lines). Symbols represent the weight loss at each follow-up point. Values were based on a mixed model that was adjusted for the treatment type and baseline age, height, weight, energy and macronutrient intakes, and their interactions with time. P-interaction values were derived from ANOVA tables (F statistics). A significant interaction term (P < 0.05) indicates that the 0.5-y change subgroups were associated with a relative weight loss over the entire follow-up time.

FIGURE 2

Mean (95% CI) relative weight loss after bariatric surgery grouped according to short-term change (≤0.5 y postsurgery) in energy and macronutrient intakes in women (n = 1130). Subgroups were divided according to changes in energy intake and macronutrient composition from baseline to the 0.5-y follow-up. For example, mean intake of carbohydrates was calculated for each time point, and participants were grouped according to tertiles of 0.5-y changes in carbohydrate intake. Similarly, mean intake of fat was calculated for each time point, and participants were grouped according to tertiles of 0.5-y changes in fat intake. Group 3 always represented the largest negative change (i.e., intake reduction; squares with dashed lines). Group 1 represents either individuals with the smallest negative change (percentage of energy) or those with the largest positive change (i.e., intake increase; circles with solid lines). Group 2 represents participants with either positive or negative intermediate changes (triangles with solid lines). Symbols represent the weight loss at each follow-up point. Values were based on a mixed-model that was adjusted for the treatment type and baseline age, height, weight, energy and macronutrient intakes, and their interactions with time. P-interaction values were derived from ANOVA tables (F statistics). A significant interaction term (P < 0.05) indicates that the 0.5-y change subgroups were associated with a relative weight loss over the entire follow-up time.

FIGURE 3

Mean (95% CI) relative weight loss after bariatric surgery on the basis of a mixed model in men (n = 480) grouped by isoenergetic changes in the proportions of carbohydrates, fat, and protein in the diet. The upper plot illustrates the relative weight loss over time in participants who favored carbohydrates over fat (squares with dashed lines) and in participants with the opposite composition (circles with solid lines). The middle plot illustrates the relative weight loss over time in participants who favored protein over fat (squares with dashed lines) and in participants with the opposite composition (circles with solid lines). In the lower plot, the relative weight loss over follow-up time is illustrated with participants grouped according to those who favored protein over carbohydrates (squares with dashed lines) and those with the opposite composition (circles with solid lines). P-interaction values between the relative weight change over time and the change categories were derived from an ANOVA (F statistics).

FIGURE 4

Mean (95% CI) relative weight loss after bariatric surgery on the basis of a mixed model in women (n = 1130) grouped by isoenergetic changes in the proportions of carbohydrates, fat, and protein in the diet. The upper plot illustrates the relative weight loss over time in participants who favored carbohydrates over fat (squares with dashed lines) and in participants with the opposite composition (circles with solid lines). The middle plot illustrates the relative weight loss over time in participants who favored protein over fat (squares with dashed lines) and in participants with the opposite composition (circles with solid lines). In the lower plot, the relative weight loss over follow-up time is illustrated with participants grouped according to those who favored protein over carbohydrates (squares with dashed lines) and in those with the opposite composition (circles with solid lines). P-interaction values between the relative weight change over time and the change categories were derived from an ANOVA (F statistics).