Ever since Dr. Robert Atkins came out with his first low-carb diet book in 1972, carbohydrate restriction has been a slam dunk for weight loss. In those early years, however, that impressive weight loss was often accompanied by fears that even though health appeared to be improving, surely all that fat—especially saturated fat—would give you a heart attack. So, sure, people were losing weight like crazy, but all that meant was they’d make slimmer corpses. Fortunately, in the decades since, an avalanche of research indicates that not only are low-carb diets not harmful for cardiovascular health, but they appear to be quite beneficial. Until recently, however, it was unknown whether the beneficial effects seen in cardiovascular health were due to the weight loss or due to the carbohydrate restriction itself. A new study out of Ohio State University indicates it’s the latter—that improvements in cardiovascular biomarkers occur even without weight loss.

The study, “Dietary carbohydrate restriction improves metabolic syndrome independent of weight loss,” involved 16 adults with obesity and metabolic syndrome. In a randomized crossover trial, they followed a low-carb, moderate-carb, and high-carb diet, each for 4 weeks with a 2-week washout period during which they returned to their habitual diet. The key factor in this study is that for all three diets, total calories were the same, and they were calculated to ensure the subjects did not lose weight.

As a percentage of total calories, protein was equal in all diets; what differed were carbs and fat:

Low-carb diet Moderate-carb diet High-carb diet Mean total calories/day 2950 2950 2950 Protein 20% 20% 20% Fat 74% 48% 23% Saturated fat 100 g/d 70 g/d 40 g/d Carbs 6% 32% 57%

After 4 weeks on the low-carb diet, more than half the participants (9 out of 16) no longer met the criteria for metabolic syndrome, compared to 3 after the moderate-carb diet and only 1 after the high-carb diet. There were no significant changes in blood pressure or fasting insulin between diets, but glucose levels were lower on the low-carb diet. And, true to intent, neither weight, nor body fat percentage nor waist circumference changed significantly on the diets, but there were substantial improvements in metabolic syndrome markers and cardiovascular risk factors after the low-carb diet, including a shift from small, dense LDL particles to larger particles (a more atherogenic profile to a less atherogenic profile), dramatic decreases in triglycerides and increases in HDL-C. Improvements also occurred on the other two diets, but they were larger after the low-carb diet. The same was true for fasting insulin and HOMA-IR: all diets improved both of these, but the low-carb diet improved them more (although the improvement in fasting insulin between the different diets was not statistically significant).

This study is important because it suggests that metabolic health—or, at the very least, biomarkers of metabolic health—can improve dramatically even in the absence of weight loss. This has been shown before, but the more clinical studies that are done, the more confident healthcare practitioners can be that it’s a true, reliable and repeatable effect and not a fluke.

The study is also important because obesity is so often blamed as the cause of type 2 diabetes, metabolic syndrome, non-alcoholic fatty liver, hypertension, gout, PCOS, and more, when the fact is, all of these conditions can and do develop in people of any body weight. It’s not about the body weight or even about total body fat; it’s about the metabolism and more specifically, it’s about carbohydrate sensitivity. As the Ohio State researchers wrote: “Obesity is often emphasized as the key factor in the pathophysiology while ignoring the perspective that MetS manifests as a carbohydrate-intolerant phenotype,” and “MetS is a pathologic state that manifests as carbohydrate intolerance.”

Study author Jeff Volek, PhD, said, “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.”

The fact that low-carb diets improve numerous aspects of health independent of weight loss should not be a big surprise. After all, people adopt low-carb or ketogenic diets for many reasons other than weight loss. People ditch the carbs as a way to manage migraines, epilepsy, other neurological disorders, and even athletes who are already healthy, lean and fit are adopting low-carb diets to support athletic performance—including record-holding ultra-endurance athletes.

This cannot be emphasized enough: metabolic syndrome and cardiometabolic disease in general occur in people of any body weight, not exclusively those who are overweight or obese. Researchers have coined the phrase “personal fat threshold” to explain the phenomenon of type 2 diabetes in people of normal body weight. For individuals affected by hypertension, dyslipidemia or elevated blood glucose (including full-blown type 2 diabetes), reducing dietary carbohydrate intake may be an effective strategy for improving these whether or not someone is already at a “normal” body weight.

Everything old is new again: it seems the much-maligned Dr. Atkins was right after all. Nutrition and health authorities are starting to acknowledge the undeniable efficacy of carbohydrate restriction for improving blood glucose management and more. The American Diabetes Association recently issued a consensus in which they stated, “Reducing overall carbohydrate intake for individuals with diabetes has demonstrated the most evidence for improving glycemia and may be applied in a variety of eating patterns that meet individual needs and preferences.” The low-carb way of eating certainly isn’t the only strategy for improving metabolic health, but at least now it can be offered as medical nutrition therapy without handwringing about potential dangers that have not come to pass after many years of thousands of people eating this way.