A series of recent clinical trials addressed a debate over the weight-control merits of low-carb versus low-fat diets.

And their results suggest that that people can shed an equal amount of weight on either diet, and kept it off for up to one year.

For example, a 2018 clinical trial found that any diet featuring whole foods — whether it’s low-carb or low-fat — will aid weight control: see Stunning Study Upsets a Big Diet Debate.

But the results of one of those recent trials — a particularly well-designed study — suggest that low-carb diets are best for longer-term weight control.

In that 2018 trial — called the Framingham State Food Study — volunteers assigned to a low-carb (20% of calories) diet for five months burned 250 more daily calories daily, versus those assigned to a high-carb (60% of calories) diet: see Low-Carb Diets Won Tough Clinical Test.

That outcome was — at least in part — likely attributable to the fact that average body levels of a hormone linked to reduced calorie-burning (ghrelin) were significantly lower in the low-carb group.

As the Framingham study’s co-lead author, Cara Ebbeling, Ph.D., said, “If this [calorie-burning] difference persists — and we saw no drop-off during the 20 weeks of our study — the effect would translate into about a 20-pound weight loss after three years, with no change in calorie intake.”

Better yet, the Framingham trial’s results showed that the participants who, at the outset of the trial, displayed released the most insulin in response to dietary carbs burned about 400 more calories per day than the people in the high-carb group.

Low-carb diet yields cardiometabolic health benefits 
The results of another, recent high-quality trial confirm prior indications that low-carb diets do more to reduce the risks for cardiovascular disease and diabetes — which are collectively called “cardiometabolic diseases”.

In that trial, a low-carb diet beat a high-carb diet for improving three key cardiometabolic risk factors (Gardner CD et al. 2018):

  • Raise blood levels of cardio-protective HDL cholesterol.
  • Lower high triglyceride levels, a key risk factor for cardiovascular disease.
  • Lower people’s dietary “glycemic load”, which reduces the risk for diabetes.

And those low-carb diet benefits have been evident for at least a decade — Swiss researchers who reviewed the clinical evidence nine years ago concluded that relatively high-fat, Mediterranean-style diets beat high-carb/low-fat diets for reducing cardiometabolic disease risk factors (Nordmann AJ et al. 2011).

Even saturated animal fat isn’t in the villain it’s been erroneously deemed for decades — thanks to the more nuanced picture of its cholesterol and overall cardiovascular impacts that’s emerged in recent years: see Saturated Fats Seen to Reduce Cardio Risk Factors.

Group wants a low-carb diet option added to USDA diet guidelines
The USDA issues new dietary guidelines every five years, and as part of the process, the agency’s independent Dietary Guidelines Advisory Committee (DGAC) invites public comments on dozens of questions it posted online.

Prompted by growing and compelling evidence that low-carb diets help prevent and alleviate cardiometabolic diseases, a group of physicians and health advocates formed the Low Carb Action Network (LCAN).

Their goal is to get the USDA to include a “true” low-carb diet in the agency’s upcoming 2020-2025 Dietary Guidelines for Americans. (Likewise, experts are urging the USDA to lift harmful, unscientific limits on the amounts of fish now recommended for children: see Kids’ Brain-Gains from Fish Beat Imagined Risks.)

To that laudable end, LCAN is promoting a grassroots campaign to ensure that the USDA’s 2020-2025 diet guidelines include a “properly defined” low-carb diet, to provide a healthful, evidence-based eating plan for the many Americans with diet-related chronic diseases — and the huge proportion at risk for them.

LCAN members point to the large and rapidly growing body of evidence — such as the trials we described above — supporting low-carb diets as an effective way to prevent and even reverse diet-related conditions such as pre-diabetes, diabetes, overweight/obesity, high blood pressure, and many others.

They note that even the notoriously conservative, slow-to-change American Diabetes Association (ADA) recently endorsed low-carb/keto diets for the prevention and management of type 2 diabetes.

And a University of North Carolina research team recently reported that only 12% of Americans are metabolically healthy, while the remaining 88% are at risk for type 2 diabetes, cardiovascular disease, or another chronic, diet-related condition (Araújo J et al. 2018).

However, the current 2015-2020 USDA diet guidelines don’t include a low-carb diet option, and the agency has ignored increasingly strong evidence that low-carb diets reduce the risk and severity of chronic cardiometabolic diseases.

The USDA currently defines “low-carb” diets as ones that derive no more than 45% of their calories from carbohydrates. In contrast, the evidence shows that a low-carb diet only yields significant cardiometabolic benefits when it gets no more than 25% of its calories from carbs.

Given the agency’s industry-friendly history, the USDA probably arrived at its bogus definition of "low-carb" diets in response to pressure from big agribusinesses that sell breads, cereals, snacks, sweets, and various goods high in refined grains and/or sugars.

LCAN's experts issue strong evidence- and experience-based statements
Dr. Eric Westman of Duke University — who serves on LCAN’s steering committee — emphasized that the current dietary guidelines aren’t optimal for most Americans and that the diet options presented to the American people should include a genuinely low-carbohydrate eating plan: “One size does not fit all. If there’s anything we’ve learned over the last four years [since the last update of the guidelines], it’s that the low-carb approach should be a viable option.”

His LCAN colleague, Dr. Mark Cucuzzella of West Virginia University, said that most of his patients have obesity and metabolic syndrome: the cluster of metabolic warning signs linked to higher risk of heart disease, stroke, and diabetes. As he said, “If the government has any responsibility to give advice on nutrition it should be focused on those who have a medical condition impacted by nutrition and provide evidence-based solutions, one being a low-carb diet.”

Dr. Nadir Ali of the University of Houston — an LCAN advisor who’s experienced in the science and practice of low-carb diets — had this to say: “As a cardiologist, I regularly prescribe a low-carb diet to treat patients with type 2 diabetes and other heart-related diseases … given the significant scientific evidence supporting this diet, it’s time for U.S. nutrition policy leaders to prescribe a low-carb option for those who are tipping into obesity, diabetes, high blood pressure and more.”

Referring to the recent, disturbing finding that 88% of Americans are at risk for cardio metabolic disease, LCAN advisor Dr. Jeffry Gerber, M.D., insisted on inclusion of a low-carb diet in the new USDA guidelines: “It is unacceptable for our nation’s nutrition leaders to exclude nearly nine out of ten adults from the guidelines, when low-carb diets provide a viable and proven solution for effectively combatting obesity and diabetes, among other conditions.”

We agree with LCAN’s expert clinicians and researchers, and urge our readers to help them press the USDA to include a genuine low-carb diet option in its upcoming 2020-2025 guidelines. Visit the LCAN website to learn more and lend your voice to the group's campaign.


  • Araújo J et al. Prevalence of Optimal Metabolic Health in American Adults: National Health and Nutrition Examination Survey 2009–2016. Metabolic Syndrome and Related Disorders, 2018; DOI: 10.1089/met.2018.0105
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