A low-carb diet may have benefits for people at risk of developing type 2 diabetes even if they don’t lose any weight, a new study suggests.
Researchers at The Ohio State University wanted to know what happens to obese people with metabolic syndrome, a precursor to diabetes, when they eat a diet low in carbohydrates but don’t shed any pounds.
They found that more than half of study participants no longer met the criteria for metabolic syndrome immediately following a four-week low-carb diet.
The new study included 16 men and women with metabolic syndrome, a cluster of factors that also put people at higher risk of heart disease and stroke.
The conditions that contribute to metabolic syndrome include high blood pressure, high blood sugar, excess body fat around the waist and abnormally low ‘good’ HDL cholesterol or high triglyceride levels.
About a third of American adults have the syndrome, according to the American Heart Association.
After eating a low-carb diet, more than half the participants – five men and four women – saw their metabolic syndrome reversed even though they were fed diets that intentionally contained enough calories to keep their weight stable.
Previous work in the Ohio State lab and elsewhere has shown that low-carb diets can be beneficial for people with metabolic syndrome and diabetes, but nutrition scientists and others have debated whether that’s a product of the diet or a product of the weight loss typically seen when people reduce carbs, said the study’s senior author, Jeff Volek, a professor of human sciences at Ohio State.
“There’s no doubt that people with metabolic syndrome and type 2 diabetes do better on low-carb diets, but they typically lose weight and one of the prevailing thoughts is that the weight loss is driving the improvements.
That was clearly not the case here,” Volek said.
“Our view is that restricting carbs even without weight loss improves a host of metabolic problems. Obviously, quality of diet matters because quantity is locked down in this experiment.”
The study appears today (June 20) in the Journal of Clinical Investigation Insight.
Over about four months, each study participant ate three month-long controlled diets – high-carb, moderate-carb and low-carb – with a two-week break between diets.
The order in which the participants ate the diets was randomly assigned.
The research team, led by research scientist Parker Hyde, ensured that the participants would not lose weight by providing them with pre-prepared meals that contained an amount of calories equal to their energy expenditure.
After eating the low-carb diet, the participants had a variety of significantly improved health measures, particularly lower triglycerides and improved cholesterol readings.
Despite the fact that the low-carb diet contained 2.5 times more saturated fat than the high-carb diet, it decreased saturated fat in the bloodstream and was associated with an increase in the size of cholesterol particles in the blood, which decreases the risk of cardiovascular disease, Hyde said.
The researchers also report evidence of increased fat-burning efficiency after a low-carb diet and an improvement in blood sugar.
They did not see statistically significant improvements in blood pressure or insulin resistance.
Three participants no longer had metabolic syndrome after the moderate-carbohydrate diet and one no longer had the syndrome after the high-carb diet.
Volek said that those results are likely explained by the fact that even these study diets – particularly the moderate-carb diet – represented a shift toward fewer carbs for study participants.
“Even a modest restriction is carbs is enough to reverse metabolic syndrome in some people, but others need to restrict even more,” he said.
Because of the study design, waist circumference was not factored in as a contributor to metabolic syndrome.
Had the participants been permitted to lose weight, it is likely that several more would have been considered free of the condition after the low-carb diet, Volek said.
This research doesn’t address the potential long-term benefits and challenges of adopting a low-carbohydrate diet, and the researchers suggest that future long-term diet studies on people with metabolic syndrome need to include low-carb diets.
What Is A Low-Carb Diet?
A low carb diet is an eating pattern that limits carbohydrate foods, such as sugary foods, flour and bread.
There are several different versions, but they are generally high in protein, fat and healthy vegetables.
The standard American diet is at least 50% carbs, which is about 300 grams per day. Low-carb diets range from about 30% down to 5%.
Given the amount of carbs in your diet is the main determinant of blood sugar levels, it makes sense that reducing carb intake could be beneficial for diabetes care (1).
Low- Carb and Diabetes: What Do Controlled Trials Show?
Randomised controlled trials are considered the “gold standard” of scientific evidence.
In this case researchers would feed one group of diabetics a standard American diet (typically 50-60% carbs), and another a strict low-carb diet for several months or more. They can then compare which group does better.
A 2015 study looked at 93 type 2 diabetic men and women for one year. Half were randomly put on a high-carb diet (53% carbs) and the others on a low-carb diet (14% carbs, less than 50 grams per day).
Each subject’s diet plan was individualised to provide a 30% calorie reduction for weight loss, and all participated in a supervised physical activity program for the year.
Both diets showed significant improvements in daily blood sugar stability, diabetes medication usage, weight loss, fat loss, insulin resistance, HDL-cholesterol and triglycerides. However, improvements were greater in the low-carb group at both 24 weeks and 52 weeks follow-up (2).
Overall HbA1c (3-month marker for blood sugar levels) was similar, but the 24-week data indicates low-carb is more beneficial in subjects who began the study with a HbA1c of 7.2% or higher.
Additionally, 52% of the low-carb group was able to reduce diabetic medication by more than 20%. Whereas only 21% of the high-carb group reduced use by the same amount.
Low-carb diets may also help lower levels of insulin-like growth factor 1 (IGF-1), which is a hormone with structural and functional similarities to insulin.
The role of IGF-1 in diabetes isn’t fully understood yet, however high levels are linked to an increased risk of type 2 diabetes.
There have been numerous other clinical trials that found low-carb diets are beneficial for diabetes management, at least for 2-4 years.
That includes for type 1 diabetics.
Provided by The Ohio State University