Home Physical Health Popular fad diets can pack a nutritional punch, new study reveals

Popular fad diets can pack a nutritional punch, new study reveals

Popular fad diets can pack a nutritional punch, new study reveals

In a recent study published in Nutrients, researchers identified the most “popular” fad dietary patterns in the United States of America (USA), evaluated their dietary quality per the Dietary Guidelines for Americans (DGA), and presented opportunities for maximizing their nutritional quality.

Study: Opportunities for Maximizing the Dietary Quality of Fad Diets. Image Credit: Creative Cat Studio/Shutterstock.com


Research suggests that most Americans follow a Westernized diet high in saturated and trans fats, sodium, sugar, and calories. Americans also overconsume refined grains, animal proteins, and alcoholic beverages.

Furthermore, around 80% of Americans habitually consume fewer fruits, vegetables, and fibers than recommended by the DGA.

Put simply, despite concerted policy-based and programmatic efforts to educate people about nutrition and healthy diets, most Americans do not follow public dietary guidelines. 

Accordingly, the population scored low on the Healthy Eating Index (HEI) from 2005 to 2016, as revealed in the DGA survey 2020–2025. Reports also suggest that 17% of American adults followed a special diet during 2015–2018.

Given the importance of dietary quality for long-term health, the quality of the American diet needs improvement. However, that requires detailed know-how of what Americans eat or popular fad diets in America.

About the study

In the present study, researchers identified the most “popular” fad dietary patterns in the USA and used the HEI scores to evaluate their dietary quality compared to the DGAs.

First, two independent researchers compiled a database of definitions and diet attributes from peer-reviewed sources, websites, popular books, and blogs, wherein they specifically used the keyword “fad diet” to identify common themes.

Common themes that appeared most frequently were then used as a framework to establish a comprehensive working definition of a fad diet.

Next, they thoroughly searched Google Trends©, using the most widely searched terms or phrases related to fad diets to identify the ‘popular’ fad dietary patterns for inclusion in the current study.

They conducted the initial search using the keyword “diet,” which returned 25 dietary patterns. However, after elimination based on duplication, relevance, and inclusion and exclusion criteria, eight fad dietary patterns made it to the final evaluation.

Then, researchers identified the specifics of each popular fad dietary pattern and their mechanism(s) of action concerning weight loss or health outcomes. These parameters were calorie limits, micronutrient compositions, restricted dietary components, required supplements, and special foods.

The researchers utilized the operationalized parameters of the popular fad dietary patterns to create one-week menus in the same way clinical dietitians devise a meal plan for patients. They ensured that the dietary quality of these menus complied with the DGAs to the maximum possible extent.

The team used the Automated Self-Administered 24 h (ASA24®) dietary assessment tool to analyze dietary intake data and determine HEI-2015 scores in the range of 0–100, where 100 indicated full and zero indicated low adherence to the DGAs.

The ASA24® tool also collected information on specific foods, portion sizes, drinks, and condiments in each sample menu, which helped the researchers calculate the means and standard deviations (SDs) per nutrient.

Based on this, they determined whether these menus met micronutrient requirements for both males and females aged 19–50 based on recommended dietary allowances (RDAs).


In the current synthesis, the team categorized the popular fad dietary patterns as least, moderately, and most restrictive.

The DGA-compliant, plant-based/vegan, and fasting diets were the least restrictive. Military, paleolithic, and low-fermentable oligosaccharides, disaccharides, monosaccharides, and polysaccharides (FODMAP) diets were moderately restrictive.

Meanwhile, the ketogenic, carnivore, and liquid diets were the most restrictive.

After maximizing adherence to the DGAs for each popular fad dietary pattern, total HEI scores ranged from 26.7 to 89.1 for Carnivore and Low-FODMAP diets, respectively. The total calorie provision was the highest and lowest in the Liquid and Carnivore Diets at 2,143 and 1,302 kcal/day, respectively.

The majority of adequacy components for fruits, vegetables, and protein had high adequacy component scores. Other popular fad dietary patterns accommodated the maximal vegetable, fruit, and protein intakes except the ketogenic, carnivore, and liquid diets. 

ASA24 classified whole grains versus refined grains according to the theoretical menus. Therefore, whole grains consistently scored low, indicating submaximal adherence in all popular fad dietary patterns. Similarly, dairy/dairy alternatives showed submaximal adherence in six popular fad dietary patterns. On the contrary, except for the DGA-compliant, military, and liquid diets, the fatty acids ratios of other fad dietary patterns scored maximum points.

On the moderation component scale, sodium scores were consistently submaximal, indicating most fad dietary patterns supplemented excessive sodium, whereas refined grain, saturated fats, and added sugar scored high, representing low consumption.

Exceptionally, the ketogenic and the carnivore diets provided high amounts of fats from animal products.

In micronutrient analysis, calcium, vitamin D, potassium, and fiber emerged as nutrients of concern due to their underconsumption by Americans.

Notably, Vitamin D was only adequately supplemented by the paleolithic diet, whereas calcium was adequate in all except the paleolithic, carnivore, and ketogenic diets.

Furthermore, potassium was adequate in all but the ketogenic and carnivore diets, which also lacked fiber. Except for carnivore and ketogenic diets, all other dietary patterns had, on average, concerns about inadequate vitamin E and vitamin D intake.


Overall, the current study analysis showed that if carefully planned to follow the DGAs to the maximal extent, some of the popular fad dietary patterns have the potential to attain an HEI score of greater than 80. 

Five fad diets reached the cut-off threshold for high dietary quality, represented by higher HEI scores. These were the low-FODMAP, vegan, military, fasting, and DGA-compliant diets. Despite problematic nutritional adequacy, the ketogenic diet also showed the potential to achieve a high HEI score.

Furthermore, this analysis suggested that making small changes within the parameters of the dietary pattern returned promising strategies for improvement in dietary quality.

To conclude, many misconceptions exist regarding the “appropriate” way to eat. However, even popular dietary patterns have the potential to promote health.