Weight and Inflammation All at Once? The "Acid Reset" Effect of a Low-Fat Vegan Diet

1. Introduction

When Japanese people hear "healthy diet," many have traditionally thought of the Mediterranean diet, characterized by olive oil and seafood. However, an article published in the British Independent on June 27, 2025, challenged this notion. The headline declared, "Vegan Diet More Effective Than Mediterranean Diet for Initial Weight Loss."independent.co.uk

2. Overview of the Research Design

The featured study was a randomized crossover trial conducted by a U.S. research team. It involved 62 overweight adults who followed ① a low-fat vegan diet and ② a traditional Mediterranean diet for 16 weeks each, with a 4-week washout period in between. The primary evaluation metric was weight change, while secondary metrics included PRAL (Potential Renal Acid Load) values and inflammation-related markers.independent.co.ukfrontiersin.org

3. Dietary Acid Load and Weight Loss

The results were clear. During the vegan phase, PRAL significantly decreased, accompanied by an average weight loss of 5 kg (about 13 pounds), whereas no significant difference was observed during the Mediterranean phase. The reduction in acid load is directly linked to the suppression of chronic inflammation, and improvements in insulin sensitivity and gut microbiota likely contributed to the weight loss. The research team concluded that "the alkalizing effect is a mechanism independent of calorie restriction."independent.co.ukfrontiersin.org

4. Delving into the Mechanism

Foods rich in animal protein contain a lot of sulfur-containing amino acids, which produce sulfuric acid during metabolism, increasing the body's acidity. In contrast, plant-based foods rich in leafy greens and fruits provide citric acid and potassium salts, releasing alkaline ions through the kidneys to restore acid-base balance. This promotes the suppression of inflammatory cytokine production and improves intestinal permeability, ultimately preventing the enlargement of fat cells—this "acid reset" is the key to the findings.frontiersin.org

5. Strengths and Limitations of the Mediterranean Diet

However, it is premature to interpret the Mediterranean diet as "defeated." Anti-inflammatory factors such as omega-9 fatty acids from olive oil, omega-3s from seafood, and polyphenols from nuts are scientifically supported. In fact, there are many reports that the Mediterranean diet reduces cardiovascular events with long-term intervention. But what this trial showed is that in terms of "short-term weight loss," the complete removal of animal products may have an advantage.sciencedirect.comtandfonline.com

6. Economic Incentives

Not only does your weight lighten, but so does your wallet—in a good way. According to a 2024 JAMA Network Open paper, switching to a vegan diet can reduce food costs by $2.4 (about 350 yen) per day, saving over $900 annually. Considering the unit price of processed meats and cheese, this figure is understandable.nypost.com

7. Supporters on Social Media

When the Independent posted the article on X (formerly Twitter), the vegan community responded with positive comments like "It's great to lose weight while protecting animals" and "Maybe my gut feels lighter because the acid load is reduced." On Reddit's r/vegan, success stories were shared, such as "You can lose weight with the power of the plate" and "If it's low-fat, you can eat until you're full and still lose weight."reddit.com

8. Skeptics on Social Media

On the other hand, in a thread on r/science, criticisms such as "The Mediterranean diet has more evidence" and "Even with a vegan diet, if it's chips and soft drinks, it's unhealthy" were raised. Posts expressing concerns about the extreme restriction of fat intake, like "A diet that almost eliminates olive oil is unrealistic," were also seen.reddit.com

9. Expert Comments

Co-author Dr. Hana Kahleova stated, "A diet centered on leafy greens, berries, and legumes beneficially alters gut bacteria, suppresses inflammation, and has a synergistic effect on weight loss." Among nutritionists, the use of supplements or fortified foods to compensate for deficiencies in B12, D, and omega-3 (EPA/DHA) is recommended, and considering environmental impact, the trend towards "plant-forward" is likely to accelerate.independent.co.uk

10. Cultural Perspective

Japanese cuisine is originally based on grains, vegetables, and legumes, making it highly compatible with veganism. Simply reducing the intake of animal products, which surged after World War II, to "Edo period levels" would dramatically lower acid load. Miso soup with komatsuna, brown rice with natto—surprisingly, "Japanese vegan" is not a high hurdle.

11. Practical Guide: Top 10 Alkaline Foods

Broccoli / Spinach / Kale / Beets / Asparagus / Carrots / Cabbage / Berries / Quinoa / Lentils. By rotating these in main dishes, side dishes, and smoothies, you can easily achieve the PRAL target of -35 mEq/day.verywellhealth.com

12. Long-term Challenges

The study period of 32 weeks is not sufficient. There are many unexplored areas, such as rebound after weight loss, muscle mass maintenance, and impacts on mental health. Additionally, in Japan, where plant protein sources are more limited compared to the West, individual circumstances like soy allergies and celiac disease need to be considered.

13. Environmental Impact

Livestock is said to account for 14% of greenhouse gas emissions. Reducing animal products and replacing the same amount of calories with legumes could reduce GHG emissions by up to 90%. Health and the planet—there's a possibility of achieving both.

14. Conclusion

In terms of short-term weight loss, a low-fat vegan diet surpassed the Mediterranean diet. However, considering long-term cardiovascular outcomes and cultural acceptability, a continuous approach of "reducing animal products and increasing plant-based foods" seems more realistic than absolutizing one over the other. Your next plate might lower not only the numbers on the scale but also the planet's temperature.