Back in June, when Time magazine ran a cover with a seductive picture of butter and a provocative headline that proclaimed: "Scientists labeled fat the enemy. Why they were wrong. by Bryan Walsh” (1). The Time article read much like the now infamous "Big Fat Lie" article in the New York Times magazine a few years earlier. That article by yet another misguided journalist (Gary Taubes) told us that the late Dr. Robert Atkins was right about foods high in saturated fat and cholesterol not promoting heart disease and it was really dietary carbohydrate that researchers like Ancel Keys and almost the entire health-science community had been misinterpreting for years. According to Walsh and Taubes, nutrition researchers had erroneously been blaming butter and other fatty animal products like cheese, eggs, and fatty meats for obesity and coronary heart disease. They told us such foods not only helped us lose weight but also could cut our risk of developing cardiovascular disease (CVD). According to Taubes, Walsh, and a growing number of low-carbohydrate (LC) diet advocates, nutrition researchers have been dead wrong about fatty animal products being unhealthful and whole grains, beans, fruits and other high-carbohydrate foods being healthful. To me, it seems like we are entering the Bizarro World of nutrition science dreamed up by writers who don’t know much about nutrition science.
It is bad enough when journalists and diet book gurus get nutrition science wrong and confuse people with their questionable “theories." When medical researchers at elite research institutes start designing studies in obviously biased ways and then inappropriately draw excessively grandiose conclusions based on their limited data, then it seems they too have become functionaries of this questionable nutrition “science." Perhaps the worst example yet appeared in the September 2014 edition of the Annals of Internal Medicine.
Enter Bazzano & Hu
Lydia Bazzano and Tian Hu teamed up to compare the impact of both their odd version of a "popular" LC diet and a version of a "low-fat" (LF) diet on body weight and CVD risk factors. The one-year study was done on a diverse population of obese subjects. In the first two sentences of the second paragraph of this report, Drs. Bazzano & Hu tell us their reason for doing this study: "Low-carbohydrate diets have become a popular strategy for weight loss and weight management in recent years; however, their cardiovascular effects are unknown” (2). This seems reasonable enough. However, it appears that the intent of this study was not to determine once and for all whether popular LC diets like those promoted by Dr. Atkins and other popular LC diet book gurus are better for weight loss and also improving CVD risk factors than a LF diet. The article itself never mentions that the LC diet used in their study was very different nutritionally than the one advocated by Dr.Atkins and other popular LC diet gurus. And one might wonder why Bazzano and Hu’s version of a LF diet was so low in unrefined plant foods, despite the fact that all advocates of real-world LF diets do not promote LF diets composed of mostly refined grains and sugars?
Do these altered LC and LF diets suggest that Bazzano & Hu were intentionally trying to bias their results in a way that would allow them to conclude: "Restricting carbohydrate may be an option for persons who are seeking to lose weight and reduce cardiovascular risk factors and should be studied further."
Here’s a better conclusion: "Restricting refined carbohydrates and eating more nuts, fish, canola oils, and olive oil instead may favorably impact blood lipids, provided significantly more weight is lost and kept off on the higher-fat diet than on a poor-quality mostly refined-carbohydrate LF diet." But would that conclusion have suggested that they've discovered something new?
When apparently-biased researchers argue the results of comparing a exceptionally healthful "Atkins-style" LC diet with an extremely unhealthful and not so "LF" version of a high-carbohydrate diet, their results really do not prove that diets higher in fatty animal products are better than a largely unrefined plant-based truly LF diet do they? Don't Bazzano & Hu know that no responsible health professionals are advocating a diet high in refined carbohydrates with just a tad less fat than a typical American diet, either for weight loss or reducing CVD risk?
Science journalist Kenneth Kraus asked Dr. Hu whether he was concerned that his study's broad conclusion might lead many people to believe that eating more saturated-fat-rich foods won't promote CVD. Dr. Hu responded with, "By far there is no direct evidence showing saturated fat causes heart disease."
Really Dr. Hu? The data in Table 2 of the Bazzano & Hu study shows the "Atkins-style" LC diet had slightly fewer grams of saturated fat in it than did their “usual American diet.” Even so, their data in Table 3 still showed no significant drop in LDL-C despite an average weight loss of 12 pounds in their healthy-as-possible version of a LC diet group. A fair question to ask Dr. Hu would be: Why on Earth did his study's dietary advice stress the consumption of mostly unsaturated fat and discourage the intake of lots of saturated- fat-rich animal products that Dr. Atkins and other LC diet gurus claim are heart healthy? If Dr. Hu really believes that saturated fat does not actually promote heart disease, does it not seem a bit hypocritical for Bazzano & Hu to be limiting saturated fat on their "modified" Atkins-style LC diet?
Bazzano & Hu claim they fed their version of an Atkins diet simply to prevent well-known adverse side effects of LC diets. However, research on the metabolic effects of a LC ketogenic diet like the one Dr.Atkins actually once advocated was shown to markedly increase total cholesterol levels by 33%, LDL-C by 49%, apoB by 57%, and TGs by 60% in children who maintained a healthy body weight after being switched from a typical American diet to the LC ketogenic diet (3).
In a study that in many ways was similar to the Bazzano & Hu study (except that their LC diet was less weird and so was much higher in saturated fat and cholesterol content than their LF diet, and their subjects lost more weight on both the LC and LF diets). In this study, the obese subjects lost far more body fat on both the LC and LF diets (32 & 25 lbs, respectively).
However, despite the much greater loss of weight on this more Atkins-like LC diet, the researchers reported that the average LDL-C level increased significantly in the LC diet but did not on the LF diet. These authors concluded: "The LC diet may offer clinical benefit to obese persons with insulin resistance as it certainly produced weight loss. However, the increase in LDL-C with this LC diet suggests this measure should be monitored” (4).
Do you think the data from this study might have convinced Bazzano & Hu to keep the saturated fat intake in their LC diet as low as possible?
Bottom Line: Perhaps in their world of nutrition “science," Drs. Bazzano & Hu may believe the increased TC, LDL-C, nonHDL-C, and apoB levels in the blood of people who achieve and maintain a healthy body weight for many years on a real-world LC diet won't promote more CVD.
However, their study does not provide convincing evidence that replacing whole grains, fruits, and beans with fatty animal products high in saturated fat and cholesterol won't promote atherosclerosis and more CVD in the long term. It may work for weight loss, but then so do other unhealthful approaches.
Real-world health professionals ought not to recommend weight loss strategies that likely cause more harm than benefit in the long term. This is likely the case for real-world Atkins-style LC diets.
For more information about LC diets, check out https://www.foodandhealth.com/cpecourses/atkins_new.php.
By James J. Kenney, PhD, FACN
- Kwiterovich PO, et al. Effects of a high-fat ketogenic diet on plasma levels of lipids, lipoproteins, and apolipoproteins in children. JAMA 2003;290:912-20
- Brinkworth GD, et al. Long term effects of a very-low-carbohdrate weight loss diet compared with an isocaloric low-fat diet after 12 months. Am J Clin Nutr 2009; 90:23-32
Stephanie Ronco has been editing for Food and Health Communications since 2011. She graduated from Colorado College magna cum laude with distinction in Comparative Literature. She was elected a member of Phi Beta Kappa in 2008.