Quality, not only quantity of nutrients in low-carbohydrate diets matter for weight loss: Study

New Delhi: Scientists have discovered links between the source and quality of macronutrients in low-carbohydrate diets (LCDs) and the resulting long-term weight changes in new research. They found that LCDs stressing high-quality proteins, whole grain-derived fats and carbohydrates, and healthy plant-based foods were significantly linked with slower weight gain in the long term. In contrast, the research from Harvard T.H. Chan School of Public Health and Brigham and Women's Hospital, Boston, US, found that LCDs emphasising animal-sourced proteins and fats or refined carbohydrates were associated with faster weight gain.

The findings are published in the Journal of American Medical Association (JAMA) Network Open. LCDs are known to hold promise for promoting weight loss and improving metabolic health. Ketogenic diets are a type of LCDs widely resorted to for achieving weight loss and have been studied to derive only 5-10 percent energy from carbohydrates. However, few studies have considered the role of food group quality in the associations between LCDs and weight outcomes, the researchers said in their study. In this study, the research team included more than 1,23,000 initially healthy individuals from across three prospective cohort studies, with an average age of 45 years. About 84 percent of the group were women.

The researchers then prospectively examined the associations between various LCDs - plant-based, animal-based, total, healthy, and unhealthy - and weight change over 20 years of follow-up. They found that greater adherence to animal-based, total (emphasising overall lower carbohydrate intake), and unhealthy LCDs was associated with more weight gain. An unhealthy LCD was one that, according to the researchers, emphasised fewer carbohydrates from healthful sources, such as whole grains, more animal protein, and unhealthy fat.

Further, a stricter adherence to healthy LCDs, defined by the researchers as an LCD emphasising less refined carbohydrates, more plant protein, and healthy fat, was found to be linked with less weight gain. The researchers also observed that factors, such as baseline BMI, were important at the individual level in weight loss outcomes. For example, they found that obese individuals with high adherence to a healthy LCD experienced 1.63 kilograms (kg) less weight gain, but participants with BMI less than 25 experienced only 0.39 kg less weight gain.

The researchers said that the findings underscored the importance of diet quality, and not only quantity, within LCD patterns for weight management. "A high-quality LCD, rich in plant-based proteins and healthy fats, was associated with slower weight gain, while a lower-quality LCD was associated with the opposite result," they wrote in their study. They also called for future research to validate these findings across more diverse populations and to elucidate the mechanisms underlying these associations.