Low-Carb Diets That Focus on Plant Protein Are Better for Weight Management, Study Says

Fact checked by Nick Blackmer

  • Eating more plant-based proteins on a low-carb diet could lead to less long-term weight gain, new research shows.

  • Conversely, low-carb dieters who relied heavily on animal-based proteins gained more weight over time.

  • In addition to low-carb vegetables like broccoli, lettuce, and zucchini, other low-carb plant-based options include avocados, nuts and seeds, and tofu and tempeh.

People who cut carbohydrates from their diet often turn to meat as a replacement, but a new study suggests that loading up on plant-based foods instead could lead to less long-term weight gain.

The research, published in JAMA Network Open, found that low-carb dieters who relied heavily on animal-based protein gained more weight over time than those embracing foods such as non-starchy vegetables and whole grains.

“The key takeaway here is that not all low-carbohydrate diets are created equal when it comes to managing weight in the long-term,” study author Qi Sun, MD, ScD, an associate professor in the Department of Nutrition at the Harvard T.H. Chan School of Public Health, said in a press release.

People who follow a low-carb diet often restrict carbohydrate-rich foods such as bread, pasta, fruit, and starchy vegetables like potatoes and legumes. Instead, they focus on obtaining calories from protein and fat.

Researchers have long linked low-carb diets with rapid weight loss, but fewer studies have examined how the eating plan affects weight in the long term.

“Our study goes beyond the simple question of, “To carb or not to carb?’” lead author Binkai Liu, a research assistant at Harvard University’s Department of Nutrition, said in the release. “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.”

Here’s what you need to know about the study, the benefits of eating plant-based foods, and how to incorporate more of them into your diet.

<p>recep-bg / Getty Images</p>

recep-bg / Getty Images

The Association Between Weight and Low-Carb, Plant-Based Diets

The study used data from 123,000 generally healthy medical professionals enrolled in several ongoing studies that began in the 1970s and 80s. Participants in the current study were between ages 25 and 65 and all followed a low-carb diet. More than 80% were women, and most were white.

Researchers analyzed reports participants filled out every four years about their eating habits and weight. Then they divided participants into categories based on their eating patterns.

The researchers found a significant association between slower long-term weight gain and diets emphasizing plant-based foods and healthy carbs and fats. On the other hand, they found a link between diets heavy in animal products or refined carbs and weight gain over time.

The associations were particularly pronounced for participants who were younger than 55, overweight or obese, or relatively sedentary.

“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,” Sun said in the release.

Toby Amidor, RD, registered dietitian and cookbook author, told Health that “the study is reflective of previous studies that promote healthy foods, including whole grains, fruits, vegetables, legumes, and other wholesome foods when on a low-carb diet.”

“Given that 90% of Americans don’t meet their daily recommendation for vegetables and 85% don’t meet their daily recommendation for fruit per the dietary guidelines, eating more plants in general on any diet, including a low-carb one, can be beneficial, especially if those foods replace higher calorie, lower nutrient-dense foods,” she said.

Benefits of Eating More Plants While on a Low-Carb Diet

If you’re following a low-carb diet, loading up on plant-based foods can provide benefits beyond potentially preventing long-term weight gain.

“The evidence has been pretty clear that we should all be eating a more plant-based diet,” Sharon Palmer, MSFS, RDN, author of The Plant-Powered Plan to Beat Diabetes, told Health. “These diets are rich in fibers, healthy fats, micronutrients, and phytochemicals with antioxidant and anti-inflammatory action.”

A bulk of research has linked the Mediterranean diet, an eating pattern emphasizing healthy fats and plant-based foods, not only with weight loss but many other health benefits, such as a reduced risk of developing heart disease, strokes, and chronic diseases such as diabetes and certain cancers. Some studies show it may even boost brain health for older adults.

It’s important to note that incorporating some animal products into your eating plan doesn’t negate the benefits of a plant-rich diet and doesn’t necessarily mean you won’t lose weight.

In fact, research has shown that adding small quantities of leaner, minimally processed animal protein could even help you stay slim. In a paper published in the journal Food and Nutrition Research in 2015, for example, researchers concluded that people who incorporate poultry meat into a vegetable-rich diet have a lower risk of becoming overweight or obese. Furthermore, a study from 2019 found a link between fish intake and a reduced chance of developing obesity.

Related: Following a 'Keto-Like' Diet Linked to a Higher Risk of Heart Disease, Study Shows

How to Eat More Plant-Based Foods on a Low-Carb Diet

While veggies like broccoli, lettuce, and zucchini might spring to mind when you imagine plant-based foods, a low-carb plant-rich diet isn’t solely about eating leafy greens and other non-starchy veggies—though they are undoubtedly nutritious choices. There are many options to choose from.

Here are some other ingredients to integrate into your diet if you’re cutting back on carbs but ramping up on plants:

  • Avocados: This fruit is low in carbs and packed with healthy fats and fiber, making it a great plant-based food to add to your diet.

  • Nuts and seeds: These are high in fiber and healthy fats and relatively low in carbs.

  • Tofu and tempeh. These soy-based products are high-protein, low-carb plant foods that can be added to various dishes.

  • Low-carb fruits: Berries, plums, peaches, and apricots are all comparatively low-carb fruits that you can enjoy in moderation.

While following a plant-based diet has general benefits, it’s always a good idea to speak to a healthcare provider before changing your eating patterns.

Some people may need to avoid certain ingredients—those with thyroid disorders, for example, may have to limit their intake of goitrogenic foods like raw cruciferous vegetables.

You can also discuss how to plan meals carefully so that you don’t miss out on essential nutrients found predominantly in animal protein: vitamin B12, iron, calcium, and omega-3 fatty acids.

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