Association between changes in carbohydrate intake and long term weight changes: prospective cohort study

Abstract

Objective: To comprehensively examine the associations between changes in carbohydrate intake and weight change at four year intervals.

Design: Prospective cohort study.

Setting: Nurses' Health Study (1986-2010), Nurses' Health Study II (1991-2015), and Health Professionals Follow-Up Study (1986-2014).

Participants: 136 432 men and women aged 65 years or younger and free of diabetes, cancer, cardiovascular disease, respiratory disease, neurodegenerative disorders, gastric conditions, chronic kidney disease, and systemic lupus erythematosus before baseline.

Main outcome measure: Weight change within a four year period.

Results: The final analyses included 46 722 women in the Nurses' Health Study, 67 186 women in the Nurses' Health Study II, and 22 524 men in the Health Professionals Follow-up Study. On average, participants gained 1.5 kg (5th to 95th centile -6.8 to 10.0) every four years, amounting to 8.8 kg on average over 24 years. Among men and women, increases in glycemic index and glycemic load were positively associated with weight gain. For example, a 100 g/day increase in starch or added sugar was associated with 1.5 kg and 0.9 kg greater weight gain over four years, respectively, whereas a 10 g/day increase in fiber was associated with 0.8 kg less weight gain. Increased carbohydrate intake from whole grains (0.4 kg less weight gain per 100 g/day increase), fruit (1.6 kg less weight gain per 100 g/day increase), and non-starchy vegetables (3.0 kg less weight gain per 100 g/day increase) was inversely associated with weight gain, whereas increased intake from refined grains (0.8 kg more weight gain per 100 g/day increase) and starchy vegetables (peas, corn, and potatoes) (2.6 kg more weight gain per 100 g/day increase) was positively associated with weight gain. In substitution analyses, replacing refined grains, starchy vegetables, and sugar sweetened beverages with equal servings of whole grains, fruit, and non-starchy vegetables was associated with less weight gain. The magnitude of these associations was stronger among participants with overweight or obesity compared with those with normal weight (P<0.001 for interaction). Most of these associations were also stronger among women.

Conclusions: The findings of this study highlight the potential importance of carbohydrate quality and source for long term weight management, especially for people with excessive body weight. Limiting added sugar, sugar sweetened beverages, refined grains, and starchy vegetables in favor of whole grains, fruit, and non-starchy vegetables may support efforts to control weight.

Fig 1

Associations between cross stratified fifths of changes in fiber and starch or added sugar and weight change. Data were pooled from three cohorts. Positive values indicate weight gain, and negative values indicate weight loss. Weight change values were calculated based on a reference participant from the Nurses’ Health Study: woman aged 55 years who had never smoked, had a body mass index of 25, watched television for 0-1 hour daily, slept for 7-8 hours daily, and had no changes in physical activity, alcohol intake, or other dietary intake during the 2006-10 questionnaire cycle. Numbers in parentheses are the median values of the groups

Fig 2

Associations of substituting major foods containing carbohydrate with weight change (kg). Data are from a multivariable adjusted model including age (continuous), questionnaire cycle (four year intervals), body mass index (continuous) at beginning of each four year period, sleep duration (≤6, 7, 8, >8 hours/day), and changes in physical activity (continuous), alcohol use (continuous), time spent watching television (baseline only in Nurses’ Health Study and Nurses’ Health Study II (0-1, 2-5, 6-20, 21-40, >40 hours/week); and also four year change in Health Professionals Follow-up Study (continuous)), smoker status (stayed never, stayed former, stayed current, former to current, never to current, current to former), total energy intake, and intake of foods not containing carbohydrate (continuous). Red indicates positive associations and blue indicates inverse associations. Numbers in parentheses are 95% confidence intervals. See supplementary table 14 for gram weights for a standard serving of different foods