Major Study Shows That Low-Carb Can Be Heart-Healthy

Major Study Shows That Low-Carb Can Be Heart-Healthy
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A major new study in The American Journal of Clinical Nutrition has shown that certain low-carbohydrate diets, even those high in saturated fats, might improve cardiovascular risk factors and insulin resistance.

In the study, 163 obese or overweight adults (70% women) were placed on a low-calorie weight loss diet and then randomized to follow one of three different maintenance diets: high-carb, low-carb, and medium-carb. All participants were given conventionally healthy foods – plenty of vegetables, olive oil, seafood, and so on. Low-carb eaters were not gorging themselves on bacon and cheese, and high-carb eaters emphasized whole grains and less-processed starches.

The results after five months were definitive: low-carb dieters enjoyed cardiovascular and metabolic improvements across the board. Low-carb dieters experienced improvements in lipoprotein insulin resistance, triglycerides, and HDL cholesterol. Critically, they did not experience any increase in LDL cholesterol, often considered the single most reliable marker of cardiovascular risk.

The medium-carb dieters also enjoyed modest improvements, whereas the high-carb dieters suffered declines in their numbers.

The Diet

The low-carb eaters in the study were not on a very-low-carb or ketogenic diet; they ate a decent amount of fiber-heavy “slow” carbs such as fruits, legumes and nuts. And while dieters enjoyed more saturated fat than most nutritionists today would advise, mostly in the form of dairy and animal fats, the majority of their fat intake was from healthy unsaturated fats like olive oil and seafood. You might consider it a somewhat low-carb spin on the Mediterranean diet.

In total, 20% of the calories in the winning diet were from carbohydrates, with 20% from protein and 60% from fat. These proportions were much less extreme than most ketogenic diets, which generally restrict dieters to take as little as 5-10% of their daily calories from carbs. Many low-carb advocates would therefore classify the tested diet as only moderately low-carb. So, while this study is a huge validation for the healthiness of carbohydrate restriction, it was identifiable as conventionally healthy, and therefore doesn’t tell us much about the more radical low-carb diets that many people with diabetes

The Impact

The news has made a splash, and received a big treatment in The New York Times. If the result is confirmed in further trials, it could have a huge impact on diabetes care, where authorities have been slow to embrace low-carb eating patterns.

There is little dispute that low-carbohydrate diets can grant patients unmatched blood glucose control. Of all the macronutrients we eat, carbohydrates prompt by far the largest blood sugar increases, and therefore require the most insulin (whether made naturally in the pancreas or injected exogenously). The experiences of innumerable people with diabetes show that carbohydrate restriction can significantly improve diabetes control.

Despite the apparent wisdom in the low-carb approach, major diabetes authorities have been reluctant to endorse low-carbohydrate eating patterns. That hesitance has been significantly driven by fears that low-carbohydrate diets, no matter how well they enhance glucose control in the short term, might eventually lead to impaired cholesterol metabolism, atherosclerosis, cardiovascular disease, and early death.

Low-carbohydrate diets are typically high-fat, almost by necessity. And while some low-fat eating approaches emphasize fat more than others, virtually anyone restricting their carbohydrates will have to compensate by eating more fat. (It would take an extraordinary amount of protein to eat a diet that was both low-carb and low-fat). And if you enjoy meat, dairy, or coconut oil, many of those fats will be saturated, long the bogeyman of the nutrition world. Saturated fat has been considered a singular risk for heart disease for decades. While scientists have largely begun to question that connection, diet authorities have moved very slowly.

Heart disease is a huge topic for people with diabetes; it’s the leading cause of death in our community. Diabetes itself is a huge independent risk factor for heart disease, as are many of the related conditions that people with diabetes tend to have, such as high blood pressure and obesity. As a result, diabetes experts always place a great deal of emphasis on heart health, which is one reason why, for example, almost everyone with diabetes is recommended to take statins.

The American Diabetes Association, the United States’ foremost diabetes authority, regularly reviews and updates its nutrition consensus report. In recent years, the ADA has taken baby steps in acknowledging the safety and efficacy of low-carb diets, in addition to other alternative diets, but has stopped short of fully endorsing extreme carbohydrate restriction as a particularly healthy way to treat diabetes. The 2019 report noted that “from the current evidence, this eating pattern does not appear to increase overall cardiovascular risk, but long-term studies with clinical event outcomes are needed.”

While the American Journal of Clinical Nutrition study does not represent the type of long-term study that can definitively link low-carb eating style to health outcomes, it is large and rigorous enough to turn heads in the nutrition world. At a minimum it should help spur more significant research into the topic.


In a major study, a high-fat and lower-carb diet that emphasized healthy ingredients was found to significantly improve heart disease risk factors and improve insulin resistance.

The successful diet avoided junk foods and grains but allowed for some consumption of “slow carbs” such as fruit, legumes, and nuts. While dieters enjoyed some red meat and dairy, the diet also emphasized wholesome ingredients such as veggies, fish, lean proteins, avocado, and olive oil.

This heart-healthy and moderately low-carb diet could have tremendous potential for people with diabetes, offering both improved cardiovascular health and tighter blood glucose control.

Diabetes Daily
Ross Wollen
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