High Carbohydrate vs High Fat Diets: Which is Preferable for Long-term Use?

Background: Commercial manufacturers have formulated diets to promote not only weight reduction but also to reduce risks of chronic diseases.

Objective: To determine if these formulations satisfy requirements for essential nutrients and their suitability for long term use.

Methods: We have selected two established commercial diets, one high carbohydrate, low fat (diet 1) and the other, low carbohydrate, high fat (diet 2) and determined "representative meals" through use of recipes suggested in the manufacturer's manuals. Nutrition Data System for Research (NDSR) software has been used to perform the most extensive nutrient analysis to date of these diets.

Results: Tables report macronutrients (energy), vitamins, minerals, essential amino acids, essential fatty acids and nutrient-related components for a total of 62 entries. Diet 1 satisfied requirements for 50 of these (81%) with only vitamin B12, vitamin D, and essential fatty acids not reaching recommended levels, while fiber and glycemic load exceeded suggested values. Diet 2 satisfied requirements for forty- six of the components (71%) but had excess percentage of fat, especially saturated fat, sodium and cholesterol as well as decreased percentage of carbohydrate resulting in suboptimal intake of B-complex vitamins (B1, niacin and total folate) as well as fiber.

Conclusions: Neither diet satisfied adequacies for all reported nutrients. However, based on nutrient content alone diet 1, if supplemented, could be sustained over the long term whereas diet 2, even if supplemented, should not be encouraged for long term adaptation.