Scintillating Findings From New Orleans: Low Carb Diet Is Better than Low Fat for Losing Weight and Preventing Heart Disease

The SC and the Significant Other of the SC at Commander's Palace following an investigation of shrimp and grits.
The SC and the Significant Other of the SC at Commander’s Palace following an investigation of shrimp and grits.

The Skeptical Cardiologist is in New Orleans this weekend on a dedicated quest to research low carb diets.

The low fat diets recommended by government guidelines and national organizations like the American Heart Association don’t help most individuals lose weight and they don’t lower  the risk of heart disease. It’s very hard to understand why these are still promulgated by these organizations.

Some diets, such as the Atkins, South Beach and Paleo diets, advocate very low carbohydrate consumption and have helped many successfully lose weight.  However, due to the high fat in such diets, there has been concern about their overall effect on  cholesterol levels and heart disease.

A new study published in the Annals of Internal Medicine addressed the question of which of these dietary  approaches is best. Researchers at Tulane University (located inNew Orleans!)  randomly divided   148 obese (BMI>30) men and women (88% were women and 51% were black) into two  groups: a low-carbohydrate group that was encouraged to consume no more than 40 grams of carbohydrates  per day (the amount of two slices of  bread), and a low-fat group, which was encouraged to consume less than 30 percent of their calories from fat and 55 percent from carbohydrates (based on the National Education Cholesterol Program guidelines).

Interestingly neither group was instructed to lower their overall calorie consumption and both groups were instructed NOT to change their overall physical activity level (the researchers were trying to minimize factors effecting their results other than the percentage of fat/carbs).

The funding source for the study was the National Institutes of Health so we can consider the study unbiased by industry.

After 12 months, the low-fat group had lost 1.8 kg (2.2lbs=1kg) and the low-carb group had lost 5.3 kg.

The low-carb group had lost 8 pounds more, a difference that was highly  statistically significant (p<.001).

In addition, in the low-carb group fat mass had declined by 1.2% whereas it had risen by 0.3% in the low-fat group.

In other words, the low-carb group was losing body fat but the low-fat group was just losing lean body mass.

My patients, like most Americans, have had the lie that fat consumption causes obesity and contributes to fatty plaques in their arteries drummed into their heads for decades and fear low-carb diets because of concerns that they will cause their cholesterol levels to rise and increase their risk of heart disease.

This new study, however, showed that the low-carb diet (with almost double the amount of saturated fat consumed compared to low-fat diet) actually improved the subjects’ heart risk profile.

Low Carb Diet Improves Cardiac Risk Profile

At 12 months, there was no difference in the total or LDL (bad cholesterol) levels between the two groups. However, the good (HDL) cholesterol had significantly increased in the low-carb group causing a decrease in the ration of total to HDL cholesterol. The low-fat group had no increase in HDL. Triglycerides dropped in both groups but significantly more in the low-carb group.

Atherosclerosis is not just related to the cholesterol profile as I have discussed here,  but it is a complex process involving multiple factors, including inflammation.  A simple blood test, the C-reactive protein or CRP tracks inflammation. The CRP dropped by 6.7 nmol/L in the low-carb group and rose by 8.6 nm/L in the low-fat group. Lower CRP levels have been associated with lower risk of cardiovascular events in multiple studies.

This was a small study (but actually one of the largest prospective dietary studies available) but really well done.

The major take home points are as follows:

  1. Low-carb diets for many are a very effective weight loss approach
  2. Low-carb diets, even with their higher saturated and overall  do not adversely effect the cholesterol profile or increase risk of heart disease.
  3. This study suggests that low-carb diets improve good cholesterol, lower inflammation and are likely, therefore, long term to reduce the risk of heart attacks and strokes.

Realistic Dietary Approaches

I have found the extremely low-carb diets such as Atkins to be very hard for my patients to follow long term.  Some modification of  the strict limits on carb consumption are necessary I think to make diets interesting and healthy.

Although the goal of this study was to have the low-carb group consume less than 40 grams, the average carb consumption was 93 grams at 6 months and 127 grams at 12 months, a much more sustainable level of carb intake.

The first and most important thing anyone can do if they  want to lose weight and improve their cardiovascular risk profile is eliminate added sugar from their diet.

Sugar-sweetened beverages are an easy first step. But equally important is avoiding foods masquerading as healthy due to their low fat content. Low-fat yogurt and smoothies, for example, are loaded with empty sugar calories. You are much better off consuming the full fat varieties as I have pointed out here.

This is the Skeptical Cardiologist signing off from beautiful New Orleans where my next investigation will be on the cardiovascular consequences of crawfish étouffée plus dixieland jazz.

 

 

12 thoughts on “Scintillating Findings From New Orleans: Low Carb Diet Is Better than Low Fat for Losing Weight and Preventing Heart Disease”

  1. In other words, the low-carb group was losing body fat but the low-carb group was just losing lean body mass. I THINK YOU USED THE SAME GROUP TWICE IN THIS STATEMENT!

      1. Difficult for the writer but easy for the reader to note such things. My wife reads whatever I write for that very reason.

  2. I read about this study on the nytimes and found it very interesting. However, it is discouraging that neither group, despite being obese, lost much weight at all.

    I would agree with you about 40 grams of carbs being unrealistic. I am pregnant and have easily been keeping carbs to 75-100 grams which I think is feasible for your average person. However, to do this I had to give up all grains.

  3. I enjoyed your perspective. I would like to point out that to concentrate on a nutrient, like carbohydrate, and try to limit that one nutrient, leads eaters to purchase different processed foods, but processed foods none the less. If one were to instead of recommending reducing carbohydrate, instead purchasing single ingredient foods–avoiding processed foods altogether, you would accomplish the low carb goal without pushing the patient into selecting foods unhealthy in other ways because they are ‘low-carb’.

    1. I agree. I highlighted that paper because many of my patients (and presumably many Americans) still believe that they need to consume a low fat diet to be heart healthy. I want to help them feel comfortable with the idea that they can consume real foods that are high in fat and saturated fat in particular. If you look at my dietary recommendations and other posts my focus is not on macronutrient content of foods but on eating real food that is not highly processed.
      However, defining what a “processed” food is can be difficult. For example, plain, full fat yogurt is milk that has undergone some processing. Most of the yogurt consumed in the US has had the fat taken out and replaced with sugar. The adjective “processed” doesn’t help to identify the less healthy of these two options. Looking at “added sugar” content, the truly empty carb, is a better way of identifying the unhealthy processed foods.

      1. Processed foods are those foods found in boxes and bags. They have health claims on the label. Food companies have coopted the idea of ‘healthy’ and use that idea to market foods that are far less nutritious than real foods. It’s harder to be on a diet than it is to change your grocery store habits. I tell people not to worry about losing weight but work on losing bad habits instead.

  4. Did the low carb group simply eat fewer calories? Seriously restricting carbohydrates means not eating high fat/high carbohydrate combinations like pizza, sandwiches, deep-fried battered anything, croissants, cookies, muffins, pie, ice cream products and almost all fast food and and snack food. Cheese and peanut butter consumption probably went way down. I’m wondering whether the low carb group may have actually had a fat intake of less than 30%.

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