Plant-Based Low-Carb Diets Linked to Slower Long-Term Weight Gain, Harvard Study Finds

[Dec. 30, 2023: JD Shavit, The Brighter Side of News]

In a groundbreaking study led by researchers at the Harvard T.H. Chan School of Public Health, the relationship between various low-carbohydrate diets and long-term weight management has been unveiled. This study, published in the prestigious JAMA Network Open, sheds light on the nuanced impact of low-carb diets and their composition on health over extended periods.

Lead author Binkai Liu, a research assistant in the Department of Nutrition, emphasized the significance of this research, stating, "Our study goes beyond the simple question of, 'To carb or not to carb?' It dissects the low-carbohydrate diet and provides a nuanced look at how the composition of these diets can affect health over years, not just weeks or months."

While previous research has established the short-term benefits of reducing carbohydrate intake for weight loss, this study delves deeper into the impact of low-carb diets on long-term weight maintenance, with a particular focus on the quality of food groups.

Utilizing data collected from the Nurses' Health Study, Nurses' Health Study II, and Health Professionals Follow-up Study, the researchers conducted a comprehensive analysis of the diets and weights of 123,332 healthy adults spanning from as early as 1986 to as recently as 2018.

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Each participant provided self-reports of their diets and weights every four years. The researchers categorized participants' diets based on their adherence to five types of low-carb diets: total low-carbohydrate diet (TLCD), animal-based low-carbohydrate diet (ALCD), vegetable-based low-carbohydrate diet (VLCD), healthy low-carbohydrate diet (HLCD), and unhealthy low-carbohydrate diet (ULCD).

The study's findings revealed a significant association between diets rich in plant-based proteins, healthy fats, and healthy carbohydrates like whole grains and long-term weight management.

Participants who increased their adherence to TLCD, ALCD, and ULCD experienced greater weight gain compared to those who favored the healthier HLCD over time. This association was most pronounced among participants who were younger (below 55 years old), overweight or obese, and less physically active.

However, when it came to the vegetable-based low-carb diet (VLCD), the results were more nuanced. Data from the Nurses' Health Study II demonstrated an association between higher VLCD scores and less weight gain over time, while the data from the Nurses' Health Study and Health Professionals Follow-up Study presented mixed results.

Senior author Qi Sun, an associate professor in the Department of Nutrition, summarized the key takeaway, stating, "The key takeaway here is that not all low-carbohydrate diets are created equal when it comes to managing weight in the long-term. Our findings could shake up the way we think about popular low-carbohydrate diets and suggest that public health initiatives should continue to promote dietary patterns that emphasize healthful foods like whole grains, fruits, vegetables, and low-fat dairy products."

This groundbreaking study highlights the importance of considering the composition of low-carb diets when assessing their impact on long-term weight management. It underscores that low-carb diets predominantly consisting of plant-based proteins, healthy fats, and whole grains are associated with better weight control over extended periods.

While previous research has primarily focused on short-term weight loss benefits associated with low-carbohydrate diets, this study bridges the gap by examining their impact on sustained weight maintenance. By analyzing data collected over several decades from a large cohort of healthy adults, the researchers were able to provide a comprehensive perspective on this dietary approach.

The study's categorization of low-carb diets into five distinct types allowed for a detailed examination of their effects. The "total low-carbohydrate diet" (TLCD) emphasized overall lower carbohydrate intake, while the "animal-based low-carbohydrate diet" (ALCD) placed a focus on animal-based proteins and fats. In contrast, the "vegetable-based low-carbohydrate diet" (VLCD) highlighted plant-based proteins and fats.

The "healthy low-carbohydrate diet" (HLCD) prioritized plant-based proteins, healthy fats, and reduced consumption of refined carbohydrates. Finally, the "unhealthy low-carbohydrate diet" (ULCD) leaned toward animal-based proteins, unhealthy fats, and carbohydrates from processed breads and cereals.

The results of this study demonstrated that diets featuring plant-based proteins, healthy fats, and whole grains were significantly associated with slower long-term weight gain.

This positive association with weight management was particularly pronounced among individuals who were younger than 55 years old, overweight or obese, and less physically active. In contrast, diets emphasizing animal-based proteins and fats, as well as those rich in unhealthy carbohydrates, were linked to greater weight gain over time.

Interestingly, the relationship between vegetable-based low-carb diets (VLCD) and weight management was more complex. While data from the Nurses' Health Study II suggested that higher VLCD scores were associated with less weight gain over time, data from the Nurses' Health Study and Health Professionals Follow-up Study yielded mixed results. This complexity may arise from variations in dietary choices and other factors that influence weight management among participants.

The research findings underscore the need for a nuanced approach to dietary recommendations, recognizing that not all low-carb diets are created equal in their effects on long-term weight control.

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