Different versions of the low-carb diet have long been favored methods for shedding excess weight, but a recent study suggests that the quality of foods consumed, rather than just the quantity of carbohydrates, fats, and proteins, play a crucial role in weight maintenance.
Published on December 27, 2023, in JAMA Network Open, the study tracked participants over several decades to investigate the impact of five distinct low-carb diets on weight management.
The study’s lead author, Binkai Liu, PhD, a research assistant in the nutrition department at Harvard T.H. Chan School of Public Health in Boston, said, “The key takeaway from our study is that not all low-carbohydrate diets are created equal when it comes to managing weight in the long-term — the quality of the food is crucial.”
Researchers discovered that diets characterized by low carbohydrate intake but high-quality proteins, fats, and a modest amount of carbohydrates from healthful plant-based sources, such as whole grains and beans, were associated with slower weight gain.
“On the other side, low-carb diets high in animal proteins and fats or refined carbs, such as those from red and processed meat, dairy products, and sugar-sweetened beverages, may lead to faster weight gain,” says Dr. Liu.
Meanwhile, a nutrition researcher and professor at Stanford Medicine in Palo Alto, California, Christopher Gardner, MD, says, “This study is brilliant in terms of helping to make it clear that ‘low-carb’ is a crude term that involves a lot of oversimplification. There are many ways to eat that could be called low-carb.”
Dr. Gardner, who was not involved in the study, emphasized that the findings highlight the significance of adopting a healthy, plant-based approach for optimal weight maintenance.
Research Tracks Dietary Habits of 120,000 Individuals Across 30 to 40 Years
The study aimed to address a gap in knowledge regarding the long-term effectiveness of low-carb diets for weight loss and the importance of nutrient quality. A meta-analysis of 25 studies published in April 2022 in Diabetes, Obesity, and Metabolism discovered that low-carb diets were linked to “greater short term weight loss than non-carbohydrate restricted diets.”
By analyzing data from the first and second Nurses’ Health Studies and the Health Professional Follow-Up Study, researchers tracked the dietary habits and weights of over 120,000 healthy adults from 1986 to as recently as 2018.
Participants provided self-reports of their diets and weights every four years via a comprehensive survey encompassing more than 130 food items, including nearly 70 items containing animal protein.
Participants’ diets were scored based on adherence to five categories of low-carbohydrate diets, all of which comprised 30 to 40 percent carbohydrates. The categories are as follows:
- A total low-carbohydrate diet simply focused on macronutrients that emphasized overall lower carbohydrate intake
- An animal-based low-carbohydrate diet, emphasizing animal-based proteins and fats
- A vegetable-based low-carbohydrate diet, emphasizing plant-based proteins and fats, including sugar and refined white flour, which are both plant-based
- A healthy low-carbohydrate diet emphasizing plant-based proteins, healthy fats, and fewer refined grains and added sugars
- An unhealthy low-carbohydrate diet emphasizing animal-based proteins, unhealthy fats, and carbohydrates coming from unhealthy sources such as processed breads and cereals
A Healthy Low-Carb Diet Was More Effective in Keeping the Weight Off
The study revealed that diets emphasizing plant-based proteins, fats, and healthy carbohydrates were significantly linked to slower long-term weight gain compared to other low-carb eating patterns.
Individuals who primarily followed unhealthy low-carb diets experienced an average weight gain of approximately 5.1 pounds over four years. In contrast, those adhering to healthy low-carb diets lost an average of about 4.9 pounds over the same period – an overall difference of 10 pounds.
These associations were particularly pronounced among participants under 55 years old, overweight or obese individuals, and those with lower levels of physical activity.
This study looks into an area of diet and nutrition that needed reassessment, says Julia Zumpano, RD, a registered dietitian at Cleveland Clinic in Ohio.
She says, “The popularity of [low-carb diets] has increased over the past decade and initially was focused on reducing carbs by replacing them with meats and high fat processed foods,” she says.
Despite the potential efficacy of low-carb diets for weight management, there are concerns about the sustainability of such approaches due to poor food choices and overly restrictive guidelines.
According to Zumpano, who was not involved in the study, individuals often experience weight regain once they stop following the diet plan.
“I found the results validating. We need to focus on diet quality, minimizing processed foods and focusing on whole foods and lean sources of protein from plant and animal sources,” she says.
Results Complement and Validate Findings from Randomized Controlled Trials
While this study provides valuable insights into the relationship between low-carb diets and weight maintenance, it is important to note that it is observational and does not establish causation. However, the study’s extensive duration and large participant cohort make it a unique and valuable resource for understanding long-term weight management.
Conducting randomized controlled trials (RCTs) for dietary interventions presents significant challenges, particularly those extending beyond six months, as participants may resist sustained changes in eating habits.
However, Dr. Gardner emphasizes the uniqueness and value of the study, noting its extensive tracking of individuals over 30 to 40 years. He emphasizes that the study addresses a critical issue: long-term weight maintenance and lifetime dietary habits – an aspect unattainable through interventional randomized controlled trials.
“These findings complement the many RCTs that have come to the same conclusion: quality of diet matters, too, not just the number of carbs,” says Dr. Gardner.
Dr. Gardner recently coauthored a 12-month randomized controlled dietary intervention published in the November 2023 copy of the American Journal of Clinical Nutrition. He notes that the significance of quality in low-carb diets, explaining that higher quality diets were linked to greater reductions in BMI as compared to lower-quality diets.
Advice on How to Eat a Healthy Low-Carb Diet from an Expert
For those considering adopting a healthy low-carb diet, Zumpano recommends seeking guidance from a registered dietitian to tailor a plan to individual needs.
She suggests prioritizing non-starchy vegetables, lean protein sources, limited quantities of whole grains, and plant based fats while avoiding processed foods and low-carb baked goods.
These are what she offers as food recommendations to begin your journey on low-carb living:
- Non-starchy vegetables (veggies other than potatoes, peas, and corn)
- Protein sources like beans and lentils, and lean animal protein like skinless poultry, seafood, Greek yogurt, cottage cheese and eggs, and limited red meat
- Whole grains in small portions (1 cup cooked 1 to 2 times per day), such as quinoa, brown or wild rice, bulgur, or millet.
- Few to no processed foods or “low carb” baked goods.
- Plant-based fats in the form of extra-virgin olive oil, avocado oil, avocados, nuts, and seeds
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