Low-fat vegan diet’s alkalizing effect linked to greater weight loss

A low-fat vegan diet yields a significant reduction in dietary acid load compared with the Mediterranean diet, and this alkalizing effect is associated with weight loss in overweight adults, according to the results of a cross-over study.

Markers of dietary acid load decreased significantly after 16 weeks on a low-fat diet. Specifically, Potential Renal Acid Load (PRAL) dropped by a mean of 28.6 mEq per day, while Net Endogenous Acid Production (NEAP) dropped by a mean of 29.9 mEq per day. On the other hand, the changes in both markers observed over 16 weeks on a Mediterranean diet were not significant (–2.8 mEq per day for both). The treatment effect of low-fat vegan diet vs Mediterranean diet on PRAL and NEAP were significant (p<0.001). [Front Nutr 2025;doi:10.3389/fnut.2025.1634215]

Results for weight loss followed the same pattern as those for dietary acid, with body weight dropping by 6.0 kg on the low-fat vegan diet and remaining stable on the Mediterranean diet (p<0.001 for treatment effect).

Notably, the reduction in dietary acid load was positively associated with weight loss, and this relationship remained significant despite adjustments for changes in energy intake (p<0.001).

“The alkalizing effect of a vegan diet may be an independent mechanism by which [the low-fat vegan diet] promotes weight loss,” the investigators said.

Previous studies have already shown that a high dietary acid load contributes to chronic low-grade metabolic acidosis, inflammation, and obesity. [Pflugers Arch-Eur J Physiol 2024;476:427-443]

“Dietary phosphorus and protein found in meat, fish, eggs, cheese, and certain grains release acid precursors. [As such,] consumption of animal proteins increases dietary acid load and induces metabolic acidosis by the accrual of non-metabolizable anions, primarily sulfate and chloride,” the investigators explained. [Nefrologia 2019;39:343-354; Clin Nutr 2011;30:416-421]

They pointed out that metabolic acidosis may contribute to weight gain through an increase in the secretion of glucocorticoids, which play a critical role in the maintenance of acid–base balance, adiposity, and insulin sensitivity. [Clin Nutr 2011;30:416-421; Kidney Int 2016;90:247-249]

“In contrast, fruits and vegetables are rich in potassium salts of metabolizable anions, which deplete hydrogen ions and therefore have an alkalizing effect. Furthermore, plant proteins are often high in glutamate, an amino acid that dissipates hydrogen ions during metabolism. Therefore, plant foods may significantly reduce the dietary acid load,” the investigators said.

The takeaway is “replacing animal products with plant-based foods like leafy greens, berries, and legumes can help promote weight loss and create a healthy gut microbiome,” according to first study author Dr Hana Kahleova from the Physicians Committee for Responsible Medicine inWashington, DC, US.

In the present study, Kahleova and colleagues recruited 62 overweight adults. These participants underwent either a Mediterranean or a low-fat vegan dietary intervention for 16 weeks. Then, after a 4-week washout period, the participants underwent the alternate intervention for another 16 weeks.

The primary outcome was change in body weight. PRAL and NEAP were measured as markers of dietary acid load, and their relationship was tested with changes in body weight.