Low-Fat vs. Low-Carb: Diets Going Head to Head

Written By: Elizabeth Daeninck, MS, RD

Title: Registered Dietitian

Alumni: Colorado State University

Last Updated on:

A recent study published in the New England Journal of Medicine in July 2008 compared three popular dietary patterns to see which one is most effective for weight loss and health benefits (including changes in cholesterol values). This study is interesting because it is one of the first to look at how these diets affect health parameters over a two-year term.

The Diet Details

Three hundred and twenty-two overweight individuals (86% of whom were male) participated in this Israeli study comparing three dietary patterns for their effects on weight loss and health factors. The diet details were as follows:

  • A low-fat diet, with no more than 30% of calories coming from fat, 10% of calories from saturated fats, and 300mg of cholesterol per day. The total calorie intakes were limited to 1500 calories for women and 1800 calories for men. These guidelines were based on the recommendations from the American Heart Association for a heart-healthy diet.
  • A Mediterranean diet, which was defined as a moderate-fat, restricted-calorie diet (1500 calories for women, 1800 calories for men). The goal with this diet was to include less than 35% of calories from fat while limiting red meat consumption, replacing it with poultry or fish. Monounsaturated fats, considered to be a healthier fat, were added to the diet through the use of olive oil and nuts. This diet pattern was based on a Mediterranean style of eating.
  • The low-carb diet was not restricted in calories as the other two test diets were. During the first two months of weight loss, participants were asked to limit their carbohydrate intake to 20 grams per day (equivalent to the carbohydrates found in one small banana), then gradually increase their intake to 120 grams per day (equivalent to 3/4 cup Raisin Bran, 2 slices bread, 3/4 cup pasta and 1 medium apple). Participants who were assigned to this arm of the study were not given any limitations on total calorie, protein, or fat intakes.

Which Diet is More Effective?

  • Weight Loss? Low-Carb and Mediterranean: Although all diet groups did lose weight, there was greater weight loss in the low-carb and Mediterranean groups. The average weight loss after two years in the Mediterranean group was 4.4 kg, while the low-carb group lost on average 4.7 kg. Interestingly, the women in the study lost the most weight on the Mediterranean diet (6.2 kg on average after 2 years, compared to 2.4 kg on the low-carb diet), while the men had more success losing weight on the low-carb diet (4.9 kg over 2 years, compared to 4.0 kg on the Mediterranean diet).
  • Cholesterol Values? Low-Carb: The low-carb diet group appeared to have the most favorable changes in cholesterol profiles; it was the most beneficial diet for changes in the HDL, triglyceride, and total cholesterol to HDL ratios.

The Low Down on the Low-Carb Diet

Given the results of this study, it seems that following a low-carb diet is the best approach for success in losing weight and improving cholesterol values. However, it is important to note that the low-carb diet prescribed in this study is not the typical low-carb Atkins-type diet which promoted eating meat. The participants following the low carb diet were encouraged to consume vegetarian sources (or plant-based) of fat and proteins, which is not the typical all-meat approach in the Atkins-type diet.

Additionally, the results indicate that the women participants in this study had more success with weight loss following the Mediterranean-style diet. However, the study did not identify the specific changes in the cholesterol values according to gender.

The Bottom Line

The data from this study may seem confusing, but it would appear that following a low-carb diet is favorable for weight loss and improvements in cholesterol profiles. Although the data reflects that women may have more success losing weight following a Mediterranean-style diet, it seems most appropriate to select a diet based on your personal dietary preferences and health needs to produce the changes necessary for your health.


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