The evidence-based positive effects of healthy eating on your weight, heart, blood sugar, digestion, and mood, plus what a healthy diet actually includes.
The positive effects of healthy eating reach far beyond the number on the scale. According to the World Health Organization, a healthy diet helps protect against malnutrition and noncommunicable diseases, including diabetes, heart disease, stroke, and cancer (1). Poor diet is a major global risk: an analysis of 195 countries estimated that 11 million deaths in 2017 were linked to dietary risks such as high sodium and low intake of whole grains and fruit (2).
Here is what research shows about how better eating affects your body and mind.
Key Takeaways
- Healthy diets help protect against diabetes, heart disease, stroke, and cancer (1).
- People who eat the most fibre have a 15% to 30% lower risk of heart disease, stroke, type 2 diabetes, and colorectal cancer (3).
- Eating more fruits and vegetables and adequate protein can support weight management (4, 5).
- Higher fibre intake increases stool frequency in people with constipation (9).
- In a randomized trial, dietary improvement helped adults with major depression (11).
What Healthy Eating Means
WHO describes four principles of a healthy diet: adequacy, balance, moderation, and diversity. A healthy diet is built on a variety of minimally processed foods that are low in unhealthy fats, free sugars, and sodium, with carbohydrates coming mainly from whole grains, vegetables, fruits, and pulses, and unsaturated fats from fish, avocado, nuts, and vegetable oils preferred over saturated and trans fats (1).
| WHO guidance for adults | Target |
|---|---|
| Fruits and vegetables | At least 400 g a day |
| Dietary fibre | At least 25 g a day, from foods |
| Free sugars | Less than 10% of daily energy (about 50 g on a 2,000-calorie diet) |
| Saturated fat | No more than 10% of daily energy |
| Trans fat | No more than 1% of daily energy |
For a practical guide to building meals, see our balanced diet guide.
1. Easier Weight Management
In a study of 80 overweight adults in a nutrition counseling program, each extra 100 grams a day of vegetables and fruits was linked to about 500 grams and 300 grams of weight loss over 6 months (4). Higher-protein diets increase fullness modestly and, in controlled studies, lead to greater weight and fat loss during calorie restriction (5). Whole grain intake is linked to lower BMI in observational studies, although short randomized trials have not shown weight loss; this analysis was funded by a cereal company (6). Our calorie deficit guide explains how to put this into practice.
2. A Healthier Heart
SaveCardiovascular disease causes almost 30% of deaths worldwide, and healthy dietary patterns such as the Mediterranean diet help prevent it, with a greater effect than single-nutrient supplements (8). Clinical trials show that higher fibre intake lowers body weight, systolic blood pressure, and total cholesterol (3). WHO advises replacing saturated and trans fats with unsaturated fats, and notes that potassium can offset some of the effect of high sodium on blood pressure (1).
3. Better Blood Sugar Control
Diets rich in whole grains, fruits, vegetables, legumes, and nuts, and lower in refined grains, red or processed meats, and sugar-sweetened beverages, reduce the risk of type 2 diabetes and improve blood sugar control and blood fats in people with diabetes (7). The quality of carbohydrates and fats matters more than their quantity (7). See our tips on how to lower blood sugar naturally.
4. Lower Risk of Chronic Disease
A series of meta-analyses in The Lancet found that people with the highest fibre intakes had 15% to 30% lower all-cause and cardiovascular mortality and lower rates of coronary heart disease, stroke, type 2 diabetes, and colorectal cancer, with the greatest benefits at 25 to 29 grams a day (3). Low intake of whole grains and fruit, and high sodium intake, were the leading dietary risks for death worldwide (2).
5. Better Digestion and Gut Health
In a meta-analysis of randomized trials, dietary fibre increased stool frequency in people with constipation, although it did not clearly improve stool consistency (9). The US Dietary Guidelines note that vegetables, fruits, fermented foods such as sauerkraut, kimchi, kefir and miso, and high-fibre foods support a diverse gut microbiome (10). Our list of high fiber foods can help you get started.
6. Support for Mood and Mental Health
SaveIn the SMILES randomized controlled trial, 67 adults with moderate to severe depression received either seven sessions of dietary support from a clinical dietitian or social support over 12 weeks, alongside their usual care. The diet group improved significantly more, and 32.3% reached remission compared with 8.0% of the control group (11). The trial was small, and diet should complement, not replace, mental health treatment.
Researchers are also studying how nutrients such as omega-3 fatty acids affect brain cells and synaptic plasticity, although much of this evidence comes from laboratory and animal research (12).
7. Healthy Habits That Last
WHO notes that dietary habits formed in childhood and adolescence often continue into adulthood, and that healthy eating throughout life helps prevent disease (1). Small, sustainable changes, such as adding a serving of vegetables or swapping refined grains for whole grains, are easier to maintain than extreme diets. For breakfast ideas based on a well-studied eating pattern, try these Mediterranean diet breakfasts.
Frequently Asked Questions
What are the positive effects of healthy eating?
Healthy eating helps prevent malnutrition and noncommunicable diseases such as diabetes, heart disease, stroke, and cancer. Diets rich in fruits, vegetables, whole grains, and fibre are linked to lower rates of these diseases, and improving diet has also helped symptoms of depression in a clinical trial.
How quickly will I notice the effects of eating healthier?
It depends on the outcome. In trials, higher fibre intake increased stool frequency, and a 12-week dietary improvement program improved depression symptoms. Changes in weight, cholesterol, and long-term disease risk build over months and years.
Can healthy eating improve mental health?
It may help. In the SMILES trial, adults with moderate to severe depression who received dietary support from a dietitian for 12 weeks improved more than those who received social support, and 32% reached remission compared with 8%. It is used alongside, not instead of, usual treatment.
What is the easiest first step toward a healthier diet?
Adding more fruits, vegetables, whole grains, and pulses is a good start. WHO recommends at least 400 grams of fruits and vegetables and at least 25 grams of fibre a day.
Do I have to give up all treats?
No. WHO recommends limiting free sugars to less than 10% of daily energy, which still leaves room for occasional treats within an overall healthy pattern.
The Bottom Line
The positive effects of healthy eating include easier weight management, a healthier heart, better blood sugar control, lower risk of chronic diseases like type 2 diabetes and colorectal cancer, better digestion, and possible benefits for mood. Focus on the basics recommended by WHO: plenty of fruits, vegetables, whole grains, pulses, and fibre, unsaturated fats instead of saturated and trans fats, and less free sugar and salt. Start with one change at a time.
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making significant changes to your diet, especially if you have an existing health condition.
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