Association between changes in carbohydrate intake and long term weight changes

1. In this prospective cohort study, the types of carbohydrates consumed were associated with long-term trends in participants’ weight. 

Evidence rating level: 2 (Good)

In this prospective cohort study, researchers aimed to examine the association between carbohydrate intake and weight changes over time. 136,432 healthy participants under age 65 were included in this study. Data were collected from the Nurses’ Health Study (1986-2010), Nurses’ Health Study II (1991-2015), and Health Professionals Follow-Up Study (1986-2014). Nutrition data were collected via repeated dietary assessments and validated questionnaires. Participants’ weight was monitored over time, with an overall trend of gaining an average of 1.5 kg every four years, and 8.8 kg over 24 years. Changes in carbohydrate intake were also calculated over time. All analyses were adjusted for many confounding variables, including physical activity, smoking, alcohol consumption, fat intake, and protein intake. Over a 4 year period, a 100 g/day increase in added sugar was associated with an average of 0.9 kgs of greater weight gain, while a 10 g/day increase in fiber intake was associated with an average of 0.8 kg less weight gain. Furthermore, greater carbohydrate intake from whole grains, fruits, and non-starchy vegetables was inversely associated with weight gain, while greater intake of refined grains and starchy vegetables was directly associated with weight gain. These associations were more pronounced for individuals who were overweight or obese compared to those with a normal BMI. The main limitation of this study is that dietary assessments relied on self-reporting. As well, researchers did not adjust for overall caloric intake as a confounding variable. Overall, this study demonstrates that the type of carbohydrates one consumes is an important aspect of weight changes over time. Physicians may use this information when counseling patients on weight, emphasizing the importance of carbohydrate quality for weight control over time. 

Click to read the study in BMJ

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