Healthy plant-based diets associated with less weight gain over time

Dr Frank Hu and colleagues from Harvard University analysed data from three large cohorts – the Nurses’ Health Study (NHS), the Nurses’ Health Study 2 (NHS2), and the Health Professionals’ Follow-Up Study (HPFS) – with a total of 126,982 adult participants.

Self-reported diet and weight data were collected at 4-year intervals over a 20-year follow-up period. The researchers assessed whether there was an association between weight gain and several plant-based diet indices:

1. Overall plant-based diet index (PDI): all plant-based foods

2. Healthful plant-based diet index (hPDI): foods rich in whole grains, fruits, vegetables, and nuts

3. Unhealthful plant-based diet index (uPDI): fruit juices, sugar-sweetened beverages, refined grains, and sweets.

On average, participants gained a mean of 0.90 kg (HPFS) to 1.98 kg (NHS2) over 4-yearly intervals. However, diets predominantly based on healthful plant foods (hPDI) were associated with significantly less body weight gain compared to diets which contained high levels of refined plant foods (uPDI):

• A 1-SD increase in PDI was associated with 0.04kg less weight gain over 4-y periods (95% CI: 0.05, 0.02 kg; P < 0.001)

• A 1-SD increase in hPDI was associated with 0.68 kg less weight gain over 4-y periods (95% CI: 0.69, 0.66 kg; P < 0.001).

• A1-SD increase in uPDI was associated with 0.36 kg more weight gain (95% CI: 0.34, 0.37 kg, P < 0.001).

Conclusion

This study demonstrates the importance of the quality of plant-based diets for weight management. Individuals who eat more healthful plant-based foods (whole grains, fruits, vegetables, nuts and legumes) are less likely to gain weight over the years compared with those who consume more refined plant-based and animal-based products.

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