What percent of vegans are underweight? An in-depth analysis

November 14, 2025 •

5 min read

Research indicates that the average vegan has a lower body mass index (BMI) than the average omnivore, but the percentage of vegans who are underweight varies by population and diet quality. In one study of Saudi adults, 25.9% of vegans were categorized as underweight, a significantly higher rate than non-vegetarians. We delve into the complex question of what percent of vegans are underweight and the reasons behind the statistics.

Quick Summary

The proportion of vegans considered underweight is influenced by numerous factors, including dietary planning, nutrient intake, and overall lifestyle. This varies significantly between studies and populations, with some research highlighting a higher prevalence of low BMI among vegans.

Key Points

Underweight Prevalence Varies: Studies show a wide range in the prevalence of underweight among vegans, with some suggesting a higher rate compared to non-vegans, while others show most maintain a healthy weight.
Lower Average BMI: Vegans consistently have a lower mean body mass index (BMI) than other diet groups, though this average is often within the healthy range.
Lower Calorie Density is a Factor: The high fiber and lower calorie density of many vegan foods can lead to reduced overall calorie intake, a contributing factor to low body weight if not managed.
Risks of Being Underweight: Being clinically underweight can increase the risk of poor bone density and fractures, particularly if nutrient deficiencies common in poorly planned vegan diets (calcium, B12) are present.
Focus on Calorie and Nutrient Density: Maintaining a healthy weight requires conscious effort to include calorie-dense foods like nuts, seeds, avocados, and plant proteins to meet energy and nutrient needs.
Monitoring is Key: Regular health monitoring and, if necessary, dietary guidance from a professional is recommended to ensure a balanced and adequate nutrient intake on a vegan diet.

Understanding the Data: Studies on Vegan BMI and Underweight Prevalence

Statistics on what percent of vegans are underweight can vary depending on the study population and methodology. While a lower average BMI is a consistent finding among vegans compared to meat-eaters, this does not automatically translate to a high rate of being clinically underweight. For example, a large cohort study known as EPIC-Oxford found that vegans had the lowest mean BMI of all diet groups, but this average BMI was still within the normal range.

However, other research has identified a higher prevalence of low BMI. A study focusing on Canadian children found that vegetarian children (some of whom may be vegan) were nearly twice as likely to be underweight as their meat-eating peers, though most were a healthy weight. Similarly, a cross-sectional study on Saudi adults revealed that 25.9% of vegans were underweight, significantly more than the 7.7% of non-vegetarians in the same cohort. These disparities underscore that generalizations are difficult and individual health is paramount.

Key Factors Contributing to Lower Body Weight in Vegans

Several factors can contribute to why some vegans may have a lower body weight or are more prone to being underweight. Understanding these can help ensure a balanced and healthy plant-based diet is maintained.

Lower Calorie Density: Many whole plant foods like fruits, vegetables, and legumes are naturally lower in calorie density and higher in fiber than animal products. This can lead to a lower overall energy intake, which, if not properly managed, can result in being underweight.
High Fiber Content: The high fiber content in a whole-foods vegan diet promotes feelings of fullness and satiety, potentially leading to reduced overall food consumption. While beneficial for weight management, it requires mindful eating to ensure enough calories are consumed.
Health Consciousness: There is some self-selection bias, as individuals who adopt a vegan diet are often more health-conscious and physically active than the general population. This combination of lifestyle factors can contribute to a lower BMI.
Potential for Nutritional Deficiencies: A poorly planned vegan diet can lead to deficiencies in key nutrients vital for maintaining a healthy weight. These can include protein, healthy fats, and certain micronutrients. Protein is essential for building and maintaining muscle mass, while healthy fats are calorie-dense and critical for hormone function.

Strategies for Maintaining a Healthy Weight on a Vegan Diet

For those who find themselves becoming underweight on a vegan diet, or those simply seeking to maintain a healthy weight, strategic dietary planning is crucial. The following list outlines key approaches:

Focus on Calorie-Dense Plant Foods: Incorporate nuts, seeds, avocados, and plant-based butters into meals to increase calorie intake without consuming excessive volume. These foods are also rich in healthy fats.
Prioritize Protein Intake: Ensure each meal includes a good source of plant-based protein, such as legumes (beans, lentils), tofu, tempeh, or high-protein grains like quinoa.
Diversify Whole Grains: Don't rely solely on low-calorie staples. Include a variety of whole grains like oats, brown rice, and whole-wheat pasta to provide complex carbohydrates for energy.
Don't Fear Healthy Fats: Include healthy plant-based oils, nuts, and seeds to help meet your caloric needs. For example, stir-frying vegetables in olive oil or topping a salad with a handful of walnuts can significantly boost calories.
Snack Smart: Mindful snacking on nutrient-dense foods between meals can prevent calorie deficits. Ideas include trail mix, edamame, or a smoothie with nut butter and fruit.

Comparing BMI Across Dietary Groups

BMI Distribution Comparison (Based on Studies)


Dietary Group	Average BMI (approx.)	Underweight Prevalence (Study Example)	Notes
Vegans	22–24 kg/m²	Variable, e.g., 25.9% in one study of Saudi adults	Lowest average BMI among all groups, but typically within normal range. Individual study results vary widely.
Lacto-ovo Vegetarians	25–26 kg/m²	Lower prevalence than vegans, but higher than non-vegetarians	Slightly higher average BMI than vegans due to inclusion of dairy and eggs.
Pesco-Vegetarians	26–27 kg/m²	Intermediate prevalence	Includes fish, contributing to a higher average BMI than vegans and lacto-ovo vegetarians.
Semi-Vegetarians	27–28 kg/m²	Intermediate prevalence	Occasional meat consumption places them closer to non-vegetarians in terms of BMI.
Non-Vegetarians (Omnivores)	28–29 kg/m²	Lower prevalence, e.g., 7.7% in one Saudi adult study	Highest average BMI and risk of obesity in many studies.

Note: These are approximations based on various studies and average BMI can differ significantly across populations.

Potential Health Risks of Being Underweight on a Vegan Diet

While a lower body weight is generally associated with some health benefits, being clinically underweight (BMI < 18.5) carries its own set of risks, which can be exacerbated by a poorly-planned vegan diet.

Lower Bone Mineral Density and Fracture Risk: Vegans often have lower intakes of calcium and vitamin D, both critical for bone health. Low BMI is independently associated with a higher risk of fractures, and combined with inadequate nutrient intake, this risk can increase significantly.
Nutrient Deficiencies: Being underweight can be a symptom of more extensive nutritional deficiencies. Inadequate intake of essential nutrients like protein, B12, and iron can lead to fatigue, anemia, and other health issues.
Compromised Immune Function: A low body weight can weaken the immune system, making individuals more susceptible to illness.

It is essential for vegans to ensure their diet is well-balanced to prevent the negative consequences associated with being underweight. Consulting a healthcare professional or a registered dietitian is always recommended, particularly for at-risk groups like children, pregnant women, and the elderly.

Conclusion

The percentage of vegans who are underweight is not a fixed number and varies based on different population studies. While many studies report a lower average BMI for vegans compared to omnivores, this isn't necessarily a negative outcome. However, a significant subset of vegans, particularly those with poorly planned diets or specific risk factors, may be underweight. By focusing on calorie-dense foods, ensuring adequate protein and healthy fat intake, and addressing potential micronutrient deficiencies, vegans can successfully maintain a healthy body weight. Regular medical check-ups to monitor nutritional status are also a crucial part of a healthy vegan lifestyle. For further reading on nutritional considerations for a plant-based diet, resources from the National Institutes of Health provide excellent guidance.

[Outbound Link: https://pmc.ncbi.nlm.nih.gov/articles/PMC7533223/]

Frequently Asked Questions

No, while studies often show vegans have a lower average BMI than meat-eaters, it is not universally true. Many factors influence body weight, including diet quality, activity levels, genetics, and overall lifestyle.

Some vegans may become underweight due to the high fiber and lower calorie density of many plant-based foods, which can lead to a lower overall energy intake. Additionally, a poorly planned diet can result in insufficient intake of protein, fats, and other key nutrients.

Being underweight can increase the risk of complications such as lower bone mineral density, a higher risk of fractures, and potential nutritional deficiencies. It can also affect immune function and overall energy levels.

To increase calorie intake, a vegan should focus on nutrient-dense, calorie-dense foods. These include nuts, seeds, nut butters, avocados, and healthy oils. Combining different plant-based proteins and whole grains also helps.

With careful planning and, in some cases, supplementation, a vegan diet can be appropriate for all life stages, including pregnancy and childhood. However, health experts emphasize the importance of monitoring nutritional status and ensuring adequate intake of key nutrients like B12, vitamin D, and iron.

A vitamin B12 supplement is considered essential for all vegans, as plant-based foods do not reliably provide it. Depending on your diet and lifestyle, you may also need to consider supplements for vitamin D, omega-3 fatty acids, iodine, or other nutrients.

Yes, it is entirely possible to be an overweight or obese vegan. While whole-food plant-based diets are often linked to lower body weight, a diet high in processed vegan junk foods, sugar, and fat can still lead to weight gain.