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

Article Information

Alan M. Preston PhD*1, Cindy A. Rodriguez BS2, Marianna M. Preston BA1

1Department of Biochemistry, University of Puerto Rico, Medical Sciences Campus, San Juan, PR 00936, USA

2NutriEtiquetas, Ciales, PR 00638 USA

*Corresponding Author: Alan M. Preston, PhD, Department of Biochemistry, University of Puerto Rico, Medical Sciences Campus, San Juan, PR 00936, USA

Received: 23 March 2023; Accepted: 03 April 2023; Published: 20 April 2023


Alan M. Preston, Cindy A. Rodriguez, Marianna M. Preston. High Carbohydrate vs High Fat Diets: Which is Preferable for Long-term Use?. Journal of Food Science and Nutrition Research 6 (2023): 24-30.

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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.


Carbohydrates; Commercial diets; Macronutrients

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Article Details


The good news is that weight reduction diets do “work” at least in the short term. A recent publication reported that all of 14 commercial diets ended up with weight loss at 6 months accompanied by favorable health results [1]. Nutrient composition of these diets varied widely among percent and types of carbohydrates, proteins, fats as well as micronutrients. The objective of our study is to determine if the manufacturers of commercial diets have formulated recipes which provided recommended dietary levels of essential nutrients that would be adequate for long-term use. To accomplish this, we have chosen two well-established commercial diets and obtained representative examples of each with use of suggested meal plans and determined nutrient adequacy with the use of software programs.

Materials and Methods


The dietary analysis is extensive using the full power of the Nutrition Data System for Research (NDSR) software of which the 2019 version contains 174 nutrients, nutrient ratios and other food components [2]. Nutrients having dietary reference index’s values (DRI’s) or recommended dietary allowances (RDA’s) will be reported. Other nutrients which can be biologically active but have no established recommendations such as phytochemicals found in plants in small amounts (polyphenolic flavonoids, carotenoids, etc) [3] and sugar alcohols, a class of polyols (sorbitol, mannitol, xylitol, etc) which are present in varying levels in many fruits and vegetables [4] will not be reported. Likewise, non-essential amino acids and other non-essential nutrients found among the 174 entities in the NDSR will not be evaluated. Finally, some nutrient-related components will be reported making a total of 62 entries.


To obtain a representative meal, we have selected at random five of the 21 suggested daily menus from our designated commercial diet manuals which contain detailed content (ingredients and portion size) for breakfasts, lunches, dinners and snacks. Diet 1 is low fat, high carbohydrate and plant-based protein [5]. Diet 2 is high fat, low-carbohydrate and moderate protein [6]. Thumbnail sketches of both diets are presented in tables 1 and 2 to portray typical menus. The actual composition of the meals can be found in the manufacturer’s manuals. The five meals are averaged (representative meal) and reported in the results section.

Table 1: Menus for Diets





Menu 1

Honeydew, Toasted

Brown rice

Vegetable platter


bread with spread

Squash, Apples

Sweet potato



Corn bread, Sherbet

Menu 2

Granola, Yogurt

Fruit salad

Spaghetti, tufu


Orange juice


Cucumber salad,

Menu 3

Grains mussili

Zucchini, Spinach

Crudite salad




Bulgar- pilof


Citrus salad

Apple crisps

Menu 4

7 grain cereal

Cauliflower -

Brussel sprouts


Orange juice

salad, Raison-breadfruit,

Green salad


Carrot soup

Raspberry ice

Menu 5

Fruit coffee cake

Cucumber-yogurt Eggplant,

Brown rice, Green salad


Orange juice

soup, Sherbert


Diet 1* Indicating [meal number] from diet manual.

Table 2: Diet 2* Indicating Week and day from diet manual (first column).






Menu 1

Cheesy bacon


Beef stroganoff

Cheese cubes

Wk 1 M

Egg muffin



Hard boiled egg




Menu 2

Keto smoothie


Beef stroganoff

Macadamia nuts

Wk 1 F




Cheese crisps

Menu 3

“Noats” coffee


Cheese tacos

Keto sno-cone

Wk 2 Th





Menu 4



Beef broccoli

Keto muffins

Wk 2 Sun


Menu 5


Bacon egg

Chicken pizza


Wk 3 F




*Daily Supplement: at least 64 oz water, 4000 mg Na, 3000 mg K, 400 mg Mg [15]


Nutrient results from the NDSR software were recorded as meal content of five recipes, selected at random, from the manufacturer’s manuals for diets 1 and 2. The average and standard deviations were calculated and compared to recommended guidelines.


A word on the manner of data presentation: When possible, we used RDA’s which are the daily dietary intake levels of nutrients considered sufficient by the Food and Nutrition Board of the Institute of Medicine to meet the requirements of 97.5% of healthy individuals in each life-stage and sex groups [7]. Because of limited space, the RDA values listed will be for adult males; females have slightly lower values. In a few instances, reference values will be expresses as adequate intake (AI), defined as recommended average daily nutrient intake [8]. Importantly, there is no RDA for energy (caloric intake) which depends on a myriad of individual factors [7]. Consequently, energy and macronutrient content will be expressed as DRI values which give a rough idea of how much energy a person should be eating each day, and how much fat, sugar, salt and so on being based on an average-sized adult doing an average amount of physical activity [9-11]. DRI values for energy have been set at 2000 Kcal for men and 1800 Kcal for women.

The sum of percentages of fat, carbohydrate and fat calories slightly exceeds the total Kcal in line 1, table 2 for both diets. This is due to the fact that calories from foods in the NDSR are determined chemically where energy values vary [12] while our calculations use standard energy values of 9, 4 and 4 Kcal/gm for fat, carbohydrates and protein respectively. There was moderate agreement in consistency of nutrient composition for most meals for diet 1, with a maximum difference of 900 Kcal between highest and lowest caloric ingestion, however, diet 2 had less agreement with a maximum difference of 9000 Kcal/gm. This caloric difference resulted in meal to meal variations of all other nutrients in the tables. Of the 62 nutrients and nutrient- like components reported, fifty-one (81%) achieved or fell within reference ranges for diet 1 and forty-six (71%) for diet 2, consequently, no further mention of these entities will be made. Components outside reference ranges, both below and above include: Diet 1. Table 2 (gm carbohydrate, %carbohydrate, fiber-all high), table 3 (vitamin D, vitamin B12 - both low), table 4 (sodium- low), table 5 (essential fatty acids all low), table 6 (cholesterol-low, glycemic load-high). Diet 2. Table 2 (gm fat and % fat, especially saturated fat-all too high, gm carbohydrate and % carbohydrate, fiber-all too low), table 3 (Vitamin D, Vitamin B1, niacin, total folate-all too low, vitamin E- slightly low), table 4 (sodium-too high), table 5 (EPA, DHA-low), table 6 (cholesterol-high). The following discussion section will include comments on the enumeration of these outliers.

Table 3: Macronutrients

Table icon

Table 4: Vitamins

Table icon

Table 5: Minerals

Table icon

Table 6: Essential Amino Acids* Essential Fatty Acids

Table icon

Table 7: Nutrient related substances

Table icon

* ≤ 400 mg (16)

T Glycemic Load (or GL) combines both the quantity and quality of carbohydrates .

Low GL is between 1 and 10; a moderate GL is 11 to 19; and a high GL is 20 or higher [18].


Diet manufacturers often shuffle proportions and types of carbohydrates, fats and proteins to create eating plans concomitant with reducing risk of major degenerative diseases commonly found in the United States. Diet 1 having low fat, high carbohydrate and plant-based protein, which the manufacturer refers to as “heart friendly”, incorporates nutrients associated with favorable cardiovascular function [13]. These include high fiber, low animal protein as well as low fat (especially saturated fat), extremely low sodium and cholesterol and little added sugar. Consequently, the aberrant values in the tables for fiber, sodium and cholesterol are a result of conscious action of the manufacturer’s design of the diet. One of the most consistent results in table 2 is percent carbohydrate (about 70%) which is probably the most important ingredient in the diet’s formulation and used as a set point. In doing this, other components may be left short of achieving reference values. The low amount of protein, especially of animal protein would account for low vitamin B12 which is exclusively formed in animals and probably the low vitamin D result since dairy products, a principle source of this vitamin, are minimized. The low amount of fat could account for diminished levels of alpha linolenic acid, especially for EPA and DHA (which measured zero) as well as for vitamin D. Finally, the high amount of dietary carbohydrate resulted in a large glycemic load. Whether this finding is of consequence or not can be elucidated by examination of which type of carbohydrates are contained in the diet. Table 2 shows natural sugars and added sugars which have high glycemic indices to be of minimal amount while fiber which has a low glycemic index to be more than ample. Meta-analyses suggest that foods with a low GI or GL may confer benefit in terms of glycemic control [14]. The quality and not the quantity in the amount of carbohydrate is the important factor as emphasized by Sievenpiper [15]. Diet 2 which is high fat, low carbohydrate and moderate protein is claimed by the manufacturer to be “fat burning” since very low carbohydrate intake (20 -35 gm/day at the start of the diet) triggers mobilization of lipid stores stimulating formation of ketone bodies which can have beside weight loss, therapeutic benefits such as reducing risk of insulin resistance and type 2 diabetes [16]. It should be mentioned at this point that our paper solely evaluates nutrient adequacy of the two diets and makes no judgment of manufacturer’s health claims. For those interested in this type of information, attention is directed to the excellent articles by Freedman et al. [17], Strychar [18] and Anderson et al. [19], the latter of which reports clinical results related to eight commercial weight reduction plans including the two diets in our study. Diet 2 has been formulated to promote ketogenic metabolism. This is accomplished by high fat content and very low amount of carbohydrate. Consequently, the aberrations in the results section for total fat, percent fat, total saturated fat, percent saturated fat, total carbohydrates and percent carbohydrates are intentionally made by the manufacturer. End results of this formulation are high dietary cholesterol and diminished intake of B-complex vitamins (Vitamin B1, niacin, total folate) and fiber which are all associated with carbohydrate content. An additional effect of low amount of carbohydrate is loss of body water. To prevent dehydration and electrolyte imbalance, at least eight glasses of water, 8 oz each are recommended accompanied by at least 4000 mg sodium (well above the DRI), 3000 mg potassium and 400 mg magnesium. Since the amount of fat and animal protein are in abundance, one would not expect reduced levels of fat-soluble vitamins or essential fatty acids as reported in table 3. A possible explanation is that the 5 meals selected missed menus that included seafood products of which several were included in the recipe manual.

Strengths of this study include the manner of data entry and diet analysis. Many dietary studies examine the amount of nutrients consumed by individuals which is susceptible to recall errors. Here we have exact ingredients and portion sizes, copied directly from the recipe books. In addition, using the full capacity of the NDSR software, we are able to perform the most extensive analyses of commercial weight loss diets to date. Potential weaknesses include estimated intake of minor nutrients and determination of a “representative meal.” The number of days to validate intake of nutrients has been established using food frequency questionnaires (ffq’s), the results of which vary widely. Macronutrients (found in table 2) can be validated within a week, while some micronutrients (tables 3 and 4) may take a month or more [20]. In regard to “reference meal”, determination was made using the average of 5 meals, selected at random from the 21 daily meals in the diet manuals. Even though recipes are formulated to produce a relatively consistent meal content, there is still a variation of 900 Kcal between highest and lowest meal energies for diet 1 and 9000 Kcal for diet 2. A “true meal” would require analysis of all 21 meals in the diet manual, however, we believe this result would not differ substantially from our estimate. Although as mentioned previously in the results section, all reference values in the tables are based solely on those of adult men and would not necessarily apply for women or children. Finally, returning to the question posed in the title of this manuscript: “High carbohydrate vs high fat diets: Which is preferable for long term use?” The answer (in this case) is “neither one as described in the recipe booklets.” For diet 1, the formulation of macronutrients resulted in suboptimal ingestion of animal protein causing a deficiency of vitamin B12 and vitamin D, and low fat also restricted vitamin D intake as well as reducing essential fatty acid content. The high level of fiber could furthermore compromise absorption of minerals. Overall, diet 1 or eating patterns of similar composition should be “safe” over a long term if accompanied with a vitamin/mineral/essential fatty acid supplement. For diet 2 the formulation of macronutrients resulted in excess amount of fat and fat associated nutrients as well as an insufficiency of carbohydrate and carbohydrate associated nutrients. To comply with DRI/RDA recommendations the formulation of diet 2 would have to be modified, reducing fat and increasing carbohydrate. This alteration however would defeat the ketogenic metabolic scheme and its purpose. Overall, diet 2 or eating patterns of a similar composition would be unsafe over the long term. Similar concern about adverse long term effects of consumption of very low carbohydrate diets has been reported in a recent review by Kirkpatrick et al [21]. In conclusion, although the two commercial weight reduction diets we have chosen differ greatly in composition and have been formulated to promote dissimilar modes of action to reducing risk for chronic diseases. They both satisfy recommendations for most nutrients, 81% for diet 1 and 71% for diet 2. The manner in which they differ is that diet 1 is sustainable over time if supplemented whereas diet 2 is not sustainable over time due to nutritional imbalances and should not be continued.


The authors would like to thank Cristina Palacios, PhD - Florida International University, Miami, FL allowing use the NDSR program as part of her grant number 1R01HD098589-01 and for her encouragement in our work.


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