Dietary fat- friend or foe? The war on dietary guidelines

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You read it in a magazine or see it on Facebook. Your neighbors and cousins are arguing about it- is low-fat/high carb a good or bad diet? Is fat a blessing or a curse? Recent research from the Harvard T. H. Chan School of Public Health Boston Children’s Hospital includes expertise and opinions on the topic and have arrived at a consensus and road map for future research. 1

Scientists came to the agreement that no one size fits all. A high-quality diet is one that is low in sugar and refined grans will help most people achieve a healthy weight and minimize risk for chronic disease.

Lead author David Ludwig, professor of the Department of Nutrition at Harvard Chan school and MD at Boston Children’s Hospital stated, "This is a model for how we can transcend the diet wars. "Our goal was to assemble a team with different areas of expertise and contrasting views, and to identify areas of agreement without glossing over differences." 1

The authors provided scientific information for three different positions on dietary guidelines for carbohydrate and fat intake. The review was published in the November issue of Science:

  1. Excessive intake of fat leads to obesity, diabetes, heart disease and possibly cancer. Low-fat diets are optimal.
  2. Refined carbohydrates produce negative effects on metabolism; lower-carbohydrate or very low-carbohydrate (ketogenic) diets with high fat content are better for health.
  3. The type of fat or carbohydrate eaten is more important to health than the relative quantity of fat or carbohydrate. 1

The scientists agreed that paying attention to diet quality such as replacing saturated and trans fat with unsaturated fats and consuming whole grains and non-starchy vegetables instead of refined carbohydrates, most people can sustain good health with varying degrees of fat-to-carbohydrate ratios. 1

Three questions were decided within the authors’ areas of disagreement that can create the groundwork of new research. These included:

  1. Do diets with various carbohydrate-to-fat ratios affect body composition (ratio of fat to lean tissue) regardless of caloric intake?
  2. Do ketogenic diets provide metabolic benefits beyond those of moderate carbohydrate restriction, and especially for diabetes?
  3. What are the optimal amounts of specific types of fat (including saturated fat) in a very-low-carbohydrate diet?

The researchers believe that discovering the answers to these questions will hopefully lead to more effective nutrition guidelines. 1

Dietitians can help their clients improve the quality of their diets by having them focus on:

  1. Reducing intake of added sugars from soft drinks, desserts, candy and other sources.
  2. Including at least 3 servings of whole grains per day such as steel cut oats, 100% whole wheat bread or pasta and quinoa, bulgur or brown rice.
  3. Substituting canola, corn or olive oil for butter or margarine in recipes.
  4. Increasing intake of leafy vegetables like kale, spinach, mustard greens and Brussels sprouts.
  5. Reducing overall fat intake by using low-fat dairy products and lean cuts of meat and fish.

Walter Willett is a co-author of the paper and professor of epidemiology and nutrition at Harvard Chan School.

Ludwig was supported in part by a career award from the National Institute of Diabetes and Digestive and Kidney Diseases (K24DK082730). Ludwig, Willett, and Jeff Volek received royalties for books about obesity and nutrition that include recommendations on dietary fat. Volek is a founder, stockholder, and consultant for VirtaHealth Corp. and a member of the advisory boards for Atkins Nutritionals Inc., UCAN Co., and Axcess Global. 1

Journal Reference:

  1. David S. Ludwig, Walter C. Willett, Jeff S. Volek, Marian L. Neuhouser. Dietary fat: From foe to friend?Science, 2018; 362 (6416): 764 DOI: 1126/science.aau2096

Submitted by Lisa Andrews, MEd, RD, LD

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