• A study finds that people eating a largely plant-based, low-carbohydrate diet are more successful at avoiding weight regain.

• The most successful low carb diet studied involved plant-based protein, fat, and less-refined carbohydrates.

• The study demonstrates that the key is not simply the amount of carbohydrates one consumes but their type and quality as well.

suggests that more than half of the weight lost in a low-carbohydrate diet returned within two years and nearly all of it by five years.

For people hoping to keep pounds at bay with a low carb sustenance diet, a new study from researchers at Harvard T.H. Chan’s School of Public Health (HSPH) in Boston, Massachusetts may help. It finds that the amount of weight one regains is influenced by the nature and quality of one’s low carb diet.

People whose low-carb diets emphasized high-quality proteins, fats, and carbohydrates from whole grains and other healthy plant-based foods were likely to regain the least amount of weight.

Conversely, people who ate more animal-sourced proteins and fats, as well as refined carbohydrates, were more likely to regain weight.

The study’s conclusions are based on data from three extensive U.S. studies, the Nurses’ Health Study (NHS) and Nurses’ Health Study II (NHSII), and the Health Professionals Follow-up Study (HPFS). The studies cumulatively extended from 1986 to 2018, with a total of 123,332 participants. Their mean age was 45, and 83% of participants were women.

Their food consumption was scored for its adherence to one of five low carb diet types:

1. a general, or total, low-carb diet (TLCD)

2. an animal-based low-carb diet (ALCD) emphasizing animal-based protein and fat

3. a vegetable-based low-carb diet (VLCD) emphasizing plant-sourced protein and fat

4. a healthy low-carb diet (HLCD) involving less-refined carbohydrates and a focus on plant protein and healthy fat

5. an unhealthy low-carb diet (ULCD) diet incorporating less-healthful carbohydrates along with more animal protein and unhealthy fat.

The researchers found that people who had obesity and more strictly followed a healthy low-carb diet experienced 1.63 kg less weight gain compared with people who had no change in their diet.

The study is published in.

Why keeping weight off is hard

Dr. Qi Sun, the study’s senior author and associate professor at HSPH, said, “It’s well-appreciated that body weight maintenance after significant weight loss is challenging.”

“It’s not necessarily due to the lack of willpower. Instead, after significant weight loss, changes in multiple hormones and systems happen and together these changes lead to reduced resting metabolic rate, enhanced appetite, increased energy intake, and ultimately weight regain,” Dr. Sun said.

“For most long-term weight loss trials, it is typical that most weight loss is achieved at about six months, and after that, there is a steady weight regain.”
— Dr. Qi Sun

Michelle Routhenstein, a preventive cardiology dietitian nutritionist, who was not involved in the study, mentioned another obvious reason for weight regain:

“Maintaining weight after losing it can be tough because oftentimes weight loss plans involve depriving oneself.” Doing without may be acceptable for a short duration but is difficult to sustain permanently.

As a cardiology-focused clinician, Routhenstein is also reluctant to prescribe low carb weight-loss regimens in any event.

“I do not recommend low-carbohydrate diets for weight loss because low-carb diets may pose heart related risks like increased coronary artery calcium, potential atrial fibrillation, and nutrient deficiencies.”
— Michelle Routhenstein

Another reason we tend to regain weight is the “set point theory.” It suggests one’s body may have a pre-set weight to which it ultimately gravitates.

The value of eating less refined carbohydrates

Another finding of the study is that those on an HLCD diet did even better than those on a VLCD diet. An important distinction between the two diets is that HLCD emphasizes less-refined carbohydrates.

According to Dr. Sun, “Refined carbohydrates and added sugars — especially those from sugar-sweetened beverages, are known to contribute empty calories without other nutrients — and “do not quickly lead to satiety.”

“They induce more rapid changes in postprandial glucose and insulin levels, lead to the feeling of hunger earlier than the intake of the same amount of calories in the form of whole grains,” he explained.

What does a successful weight maintenance strategy look like?

“I think ‘quality,” said Dr. Sun, “is the keyword in our take-home message.”

“When the low carb diets emphasize the quality of food sources of macronutrients,” he noted, “we see that such diets lead to most favorable outcomes of weight management, whereas the unhealthy version of the low carb diets show the opposite health effects.”

“As such, low-carb diets may or may not help with weight management unless they emphasize a high diet quality.”
— Dr. Qi Sun

“Transitioning from weight loss to maintenance is about making lasting habits. Create an adaptable plan, stay reflective, and lean on support systems. Staying resilient and kind to yourself is also an important component for long-term success,” Routhenstein pointed out.

Dr. Sun said that low carb diets also had to think about macronutrients “increasing macronutrients to make the total energy constant.”

Plant-based vs. animal-based low carb diets

“Plant-based diets, whether very low calorie or higher-calorie, may lead to less weight gain over time compared to animal-derived low carb diets due to their high fiber content fostering satiety, lower energy density enabling larger portions with fewer calories, and lower saturated fats,” said Routhenstein.

“Additionally, their nutrient richness and potential positive impact on the gut microbiome contribute to better weight management,” she said.

Routhenstein also strongly recommends working with a qualified healthcare professional — such as a registered dietitian — to devise a food plan that meets your individual needs.