What Percentage of Diseases Are Caused by Diet?

December 7, 2025 •

3 min read

According to the World Health Organization (WHO), poor diet and a lack of physical activity are among the leading global risks to health. While there is no single percentage for what percentage of diseases are caused by diet, evidence shows a major, quantifiable link to chronic conditions like heart disease, cancer, and type 2 diabetes.

Quick Summary

Poor diet is a leading global risk factor for disease, contributing to a significant portion of preventable chronic illnesses such as heart disease, cancer, and diabetes, but attributing a single percentage is complex.

Key Points

Poor diet is a leading risk factor: One in five deaths globally is linked to poor diet, making it a major modifiable risk factor for chronic diseases.
No single percentage exists: Attributing an exact percentage is complex due to other factors, but its contribution is significant across multiple diseases.
Associated with major chronic illnesses: Unhealthy dietary patterns are strongly linked to cardiovascular disease, type 2 diabetes, and certain types of cancer.
Specific disease links: Research suggests poor diet contributes to over 30% of certain cancers and up to 75% of some type 2 diabetes cases.
Healthy diets prevent disease: A diet rich in fruits, vegetables, and whole grains protects against many noncommunicable diseases and conditions.
Dietary components matter: Factors like high sodium, low whole grains, and high processed foods are major culprits in increasing disease risk.

The Overwhelming Evidence Linking Diet and Disease

Determining the exact percentage of diseases caused by diet is complex, as health is influenced by many factors, including genetics, environment, and physical activity. However, large-scale studies show dietary choices are a major modifiable risk factor. For instance, a 2019 study published in The Lancet found that one in five deaths globally is associated with a poor diet. The Institute for Health Metrics and Evaluation (IHME) reported that 10.6% of all deaths in 2021 were associated with poor diet, with cardiovascular disease being the leading cause. These figures highlight the profound impact of nutrition on global public health.

How Poor Dietary Choices Drive Chronic Disease

The link between poor diet and chronic disease is multi-faceted. Consuming diets high in sodium, trans fats, added sugars, and processed foods contributes to a range of health issues. For example, excessive sodium intake leads to high blood pressure, increasing the risk of heart disease and stroke. Similarly, a high intake of added sugars and refined carbohydrates is a key driver of type 2 diabetes. In contrast, a diet rich in fruits, vegetables, whole grains, and healthy fats is protective against these same conditions.

Specific Chronic Diseases Linked to Diet

Evidence from various sources provides specific percentages for the role of diet in certain diseases. Here are some examples:

Cardiovascular Disease: The IHME reported that 30% of deaths from cardiovascular disease in 2021 were attributed to poor diet. Other data suggests more than two-thirds of heart disease deaths worldwide could be prevented with healthier dietary patterns.
Type 2 Diabetes: Some studies attribute up to 75% of type 2 diabetes cases to an unhealthy diet, particularly those high in added sugars and refined carbohydrates.
Cancer: The American Institute for Cancer Research (AICR) estimates that more than 30% of cancers are directly attributable to poor diet.

The Importance of a Balanced Dietary Pattern

The composition of a healthy diet is a significant factor in disease prevention. Medical and health organizations consistently recommend increasing consumption of nutrient-dense foods while reducing ultra-processed options. The World Health Organization's recommendations include eating at least 400g of fruit and vegetables daily and limiting intake of saturated fats, trans fats, free sugars, and salt. This balance is not just about avoiding unhealthy foods but actively incorporating protective elements into one's diet.

Diet-Related Disease Risk Factors: A Comparison


Risk Factor	Associated Chronic Conditions	Impact on Health	Contribution to Early Death	Modifiability
High Sodium Intake	Hypertension, heart disease, stroke	Increases blood pressure	Significant, a leading dietary risk factor globally	High
Low Whole Grain Intake	Cardiovascular disease, type 2 diabetes	Increases risk of metabolic disorders	High, noted as a leading risk factor in some regions	High
High Processed Meat	Type 2 diabetes, certain cancers	Increases inflammation, alters metabolic health	Moderate to high, depending on consumption level	High
High Added Sugars	Type 2 diabetes, obesity, CVD	Contributes to weight gain and insulin resistance	Significant, especially related to metabolic syndrome	High
Low Fruit/Vegetable Intake	CVD, neoplasms, diabetes	Deprives body of essential vitamins and fiber	High, a major risk factor for several chronic diseases	High

The Path Forward: Promoting Healthier Eating

Addressing the high percentage of diseases caused by diet requires comprehensive public health approaches. These include education, policy changes, and creating environments where healthy eating is accessible and affordable. Initiatives can include clearer food labeling, regulating marketing of unhealthy foods, and promoting school nutrition programs. Such interventions are crucial for tackling the burden of diet-related chronic illnesses.

Conclusion

While a single number for what percentage of diseases are caused by diet is elusive, the evidence overwhelmingly indicates that poor nutrition is a primary driver of chronic disease worldwide. Research from bodies like the IHME, AICR, and WHO consistently show that dietary factors are among the most significant modifiable risk factors for preventable deaths and illnesses. By focusing on healthier dietary patterns, individuals can significantly reduce their risk of developing conditions like heart disease, type 2 diabetes, and certain cancers, highlighting the powerful role of food in determining long-term health outcomes.

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Frequently Asked Questions

Globally, high sodium intake is identified as one of the most impactful dietary risk factors, significantly increasing the risk of hypertension, heart disease, and stroke.

Yes, poor diet is a known risk factor for several types of cancer. The American Institute for Cancer Research estimates that more than 30% of cancers are directly attributable to poor dietary choices.

Studies suggest that a substantial portion of heart disease is preventable through healthier diets. Some data indicates that more than two-thirds of global deaths from heart disease could be prevented with healthier dietary patterns.

For type 2 diabetes, diet is a significant driver. Some studies suggest that up to 75% of type 2 diabetes cases can be attributed to an unhealthy diet high in added sugars and refined carbohydrates.

According to some global studies, poor diet is responsible for more deaths annually than smoking, making it a leading risk factor for deaths worldwide.

Preventive dietary changes include increasing intake of fruits, vegetables, whole grains, and healthy fats, while reducing consumption of sodium, added sugars, and processed foods.

While it can be a critical part of treatment and can significantly improve outcomes, reversing chronic disease depends on the specific condition, its severity, and other lifestyle factors. Dietary changes can, however, play a crucial role in managing and improving symptoms.