Tough limits on carbohydrates in your meals can help get type 2 diabetes under control -- but the benefits typically wane over time, a new research review shows.
The analysis of 23 small trials found that low-carb diets worked better than other eating plans in helping people lose weight and send their type 2 diabetes into remission. That was true, at least, in the first six months.
By the one-year mark, most of the advantages of the low-carb lifestyle had vanished.
It's not clear why, according to Grant Brinkworth, one of the researchers on the review. But it's possible people had a tough time sticking with the diets.
Diet changes, in general, are often hard to sustain, said Brinkworth, a senior researcher with the Commonwealth Scientific and Industrial Research Organization, Australia's national science agency.
That said, people with type 2 diabetes might be able to kick-start some weight loss and better blood-sugar control with a low-carb diet, according to Brinkworth.
"The findings of this study suggest, at least in the short term up to six months, that people with type 2 diabetes could consider a low-carb diet as a treatment option," he said.
They should do that, Brinkworth added, in consultation with their doctor -- who can adjust their diabetes medication as needed.
In the United States alone, more than 34 million people have diabetes, according to the U.S. Centers for Disease Control and Prevention. The vast majority have type 2 diabetes -- which arises when the body loses its sensitivity to the blood-sugar-regulating hormone insulin.
Type 2 diabetes is often related to obesity, and diet changes, exercise and weight loss are cornerstones of managing it.
Low-carb diets are often promoted for weight loss and reining in blood sugar. But exactly how effective they are in the long run is unclear.
The new analysis, published Jan. 13 in the journal BMJ, pooled the results of 23 clinical trials involving more than 1,300 people that tested low-carb diets against other options -- often a low-fat diet. Some trials restricted carbs to 25% or less of people's daily calorie intake; others kept carbs below 10% of daily calories.
Overall, Brinkworth's team found, low-carb diets were winning at the six-month mark: People on those plans had lost, on average, about 7.5 pounds more than those on comparison diets, and their triglycerides (a type of blood fat) were lower.
In trials that looked at diabetes remission, 57% of people on low-carb plans had gone into remission, versus 31% of people on other diets. Remission meant that a person's average blood sugar in the past three months was below the threshold for diagnosing diabetes.
By the 12-month point, however, most of the advantages of low-carb diets had vanished.
"Despite the benefits for blood-sugar control that very low-carb diets can offer, they can be very difficult to adhere to," said Julie Stefanski, a registered dietitian and certified diabetes educator. She was not part of the study.
The fact is, carb-rich foods are pleasurable, hard to avoid and offer "emotional connections to our pasts," said Stefanski, who is also a spokeswoman for the Academy of Nutrition and Dietetics.
Beyond those hurdles, Stefanski said, tight limits on carbs can end up depriving people of some nutrients, including fiber and certain vitamins.
"To be successful on a very low-carbohydrate diet, people really need a game plan to tackle all of the issues that come up," Stefanski said.
She agreed, though, that starting with a strict low-carb plan, then transitioning to a moderate diet, can work. Stefanski also agreed that people with type 2 diabetes should first talk to their doctor -- and possibly consult a dietitian about crafting a low-carb diet.
Across the studies, low-carb plans did appear safe in the short term. The one red flag appeared at the one-year point, when people on the diets tended to show an increase in their LDL cholesterol (the "bad" kind).
It's unclear, though, what that could mean for their health, Brinkworth said.
In the end, Stefanski said, there is no one-size-fits-all diet for people with diabetes.
Nor are all carbohydrates created equal. Stefanski said that a diet high in vegetables and other fiber-rich foods may help ease inflammation and benefit people with diabetes.
The American Diabetes Association has a primer on carbohydrates.
SOURCES: Grant Brinkworth, PhD, senior principal research scientist, Commonwealth Scientific and Industrial Research Organization -- Health and Biosecurity, Sydney, Australia; Julie Stefanski, MEd, RDN, spokesperson, Academy of Nutrition and Dietetics, Chicago; BMJ, Jan. 13, 2021, online