With alarming morbidity and mortality related to obesity including cardiovascular disease, diabetes, and other chronic conditions, healthy weight management remains a priority in healthcare. As a result, approaches and opinions about the best weight reduction protocol abound and trend in what often seems like capricious and hard to follow surges, at times driven more by celebrity endorsement than science.
Registered Dietitians, food and nutrition experts who have met rigorous academic and professional requirements to achieve and maintain the credential, follow not only the science but popular diet trends as well to best position themselves as evidenced-based counselors and agents of demystification and de-mythification. To that end, the recent study Effects of Low Carbohydrates and Low Fat Diets that appeared in the Annals of Internal Medicine is a welcome piece of evidence in an often contentious debate centered around macronutrient contribution, in other words the relative ratios of fat, protein, and carbohydrate to total intake.
The new study1 was financed by the NIH and included a racially diverse group of 150 men and women, assigned to follow diets for one year that limited the amount of carbohydrate or fat they were allowed, but did not formulaically attempt to limit calories. The focus on macronutrients over energy intake indirectly addresses the “calorie is a calorie” deliberation which so often finds itself at the center of the weight loss debate. In other words, does the energy balance theory (eat more than you need you gain weight, eat less than you need you lose weight) prevail or may there be other influences at play? Could there be something to the specific dynamic action of nutrients (their inherent cost to digest and metabolize), or perhaps simply a potent contribution to satiety, that tips the scale in favor of one diet over another for weight loss?
The case for a healthy, balanced lower carbohydrate diet continues to build and this study (while it won’t end the discussion) is a powerful “slam dunk” for lower carbs in the game of both weight loss as well as meaningful reductions of cardiovascular risk factors. In other words weight loss doesn’t have to undermine improved health here – you can get both. Compared to the low-fat diet, the low-carbohydrate diet subjects had greater improvements in body composition, HDL cholesterol level, ratio of total-HDL cholesterol, triglyceride level, CRP (a marker of inflammation) level, and an estimated 10 year CHD risk using the Framingham risk score. While the debate is far from over, this study, due to its rigorous design and statistically significant results, certainly pushes the conversation toward the steak and away from the low-fat pasta.
From the Registered Dietitian perspective, especially those savvy to the biochemistry and pathophysiology of lipids, the study comes as little surprise. “We have known about the relationship between refined carbohydrates and atherosclerosis for a long time,” explains Dominique Adair, Clinical Health Coach Manager – Program Development for Health Diagnostic Labs, Inc. But the Ancel Keys’ legacy — that a diet low in fat means less “fat” in your blood — has been exceptionally hard to uproot. For reasons that span from food politics (grain growers are a powerful group of lobbyists) to the challenges (and cost) of conducting well designed clinical trials in diet-disease relationships, the low-fat/fat-free paradigm has fervently resisted change Unfortunately, it is some of the dietetic “authorities” that have demonized fat for years, who have protected fat’s top spot on the bad guy list. “Whether it is simply flawed logic,” explains Adair — I want to be less fat so I need to eat less fat — or the over-investment in the calorie balance theory – At 9 kcal/g fat is the most energy dense nutrient and so it must therefore present the heftiest contribution to energy surplus problem – It has been hard to displace fat as the bad guy.
Any solid RD knows that there is no single weight loss protocol for everyone, but with the studies such as this, we can engage in an intelligent dialogue that is driven by more by research and clinical expertise than food industry lobbying to develop individualized recommendations that have the potential to produce weight loss and reduce risk factors. Armed with this study, registered dietitians and other lifestyle counselors are in a fantastic position to promote the results which did not suffer from the small sample size and low completion rates of many previous studies. “We can (and should) still recommend fruits and vegetables as low-energy density, high-nutrient density choices, but if we replace carbohydrates with protein and fat we will impose greater satiety, greater variety, and per this study a host of weight loss and disease reduction benefits. What’s more, we will not have to ask people to count calories which will be a great disappointment to no one.