Dietary acidity: Is it the secret to weight loss?

Participants in a new study on lowering ‘dietary acidity’ lost about 6kg in weight. This is how it’s thought to work.

This might be very good news for those who want to lose weight, but don’t want to be told to eat less.

A new study has found that avoiding foods that raise levels of acidity in the body could be the latest way to drop excess pounds.

Research published in the science journal Frontiers in Nutrition suggests that a high intake of foods that cause acid to accumulate in the body is associated with chronic inflammation, which upsets metabolism and might contribute to weight gain.

Participants in the study lost almost a stone in weight over 16 weeks, while the Mediterranean diet left weight unchanged.

A build up of acid in the body increases what is termed your dietary acid load (DAL).

It’s not the acidity of a food itself that determines whether it is acid-forming, but the by-products created when the body digests it.

At the top of the scale of acid-forming foods are refined and processed, but also those containing animal protein such as meat and cheese. At the bottom are the relatively alkaline-forming fruit and vegetables.

Fruit and vegetables are alkaline foods.

In the new trial, conducted by researchers at the Physicians Committee for Responsible Medicine, the University of Utah and George Washington University and involving 62 overweight adults, dieters were asked to follow either a Mediterranean-style approach including some meat and fish or a low-fat vegan diet for four months. They completed a four-week cleansing period before following the other diet for an additional 16 weeks.

All participants recorded everything they ate and their dietary records were then analysed to estimate their DAL. According to the researchers, the vegan plan not only produced a significantly lower DAL but resulted in an average 13.2lb weight loss compared with none with the Mediterranean-style approach. “Our research found that the decrease in DAL for those following the low-fat vegan diet was associated with weight loss, independent of [total] energy intake,” says lead author Dr Hana Kahleova, director of clinical research at the Physicians Committee for Responsible Medicine and the author of more than a dozen scientific studies on nutrition.

“[We found that] eating a diet that replaces animal products with more alkaline foods, including fresh fruits, vegetables, and legumes might reduce inflammation associated with weight gain.”

Francesca Crowe is a nutrition researcher and associate professor of epidemiology and health informatics at the University of Birmingham, who has researched the effects of DAL on human health. “The scientific consensus is that diet does not significantly change blood pH [a measurement of acidity or alkalinity] as it is tightly regulated within the normal range of 7.35 to 7.45 in healthy individuals,” Crowe says. However, even without that, there are suggestions that diet might affect the body’s acidity levels in other ways – measured through blood and urine samples – including having an effect inside our cells.

“Some studies have proposed the concept of low-grade metabolic acidosis, a state where acid accumulates in the body without causing a measurable change in blood pH,” Crowe says.

“It is thought that this acid retention occurs within cells and in the interstitial fluid that surrounds tissues.” When this happens, the theory is that it leads to the kind of chronic inflammation linked not just to weight gain but other health problems including cognitive decline.

“This study adds to the body of evidence suggesting that reducing DAL may support weight management,” says Dr Linia Patel, a registered dietitian and researcher in the department of clinical sciences and community health at the Universita degli Studi di Milano in Italy. However, she says, it’s hard to determine whether the weight-loss benefits that come from eating more fruit, veg and pulses are down to the fact that they are less acid-forming in the body or, as many experts maintain, “simply because they provide filling fibre, nutrients and phytochemicals profile that also help with weight loss and health”.

Other studies have suggested that DAL could be implicated in specific health issues. A 2025 paper in the International Journal of Cardiology Cardiovascular Risk and Prevention suggested that “a more acidic diet may contribute to the progression of atherosclerosis”, a thickening of the arteries that is a risk factor for heart disease, while another recent study in Scientific Reports concluded that eating to reduce DAL “may be a promising strategy for managing knee osteoarthritis, especially in ageing populations”.

People who eat more vegetables and pulses have healthier habits, it was noted.

Crowe and scientists at Babol University of Medical Sciences in Iran recently published their own findings in the journal Nutrition Reviews, which suggested a “higher acid-forming” diet was associated with a raised risk of type 2 diabetes and “overall cancer”. Crowe stresses that the findings were based on many studies that used self-reported diet data.

“People who consume more fruits and vegetables with a low DAL often engage in other healthy behaviours as well,” she says. “Although the studies included in our review adjusted for some of these factors, it is hard to determine whether the observed associations are truly due to DAL or to other healthy behaviours, including different aspects of someone’s diet.”

Some may remember the so-called alkaline diet being a celebrity diet fad in the early 2000s, with Victoria Beckham, Gwyneth Paltrow and Jennifer Aniston reported to have tried it. It fell out of favour thanks to inaccurate claims that it could change the pH of blood, reducing the risk of chronic disease. It’s increasingly clear that the benefits from such a diet are linked to established advice to consume less processed and refined food and more fruit, vegetables and pulses. “Reducing DAL may be a contributor when you increase your intake of wholesome and natural foods,” Patel says.

Gwyneth Paltrow reportedly tried the alkaline diet in the early 2000s. Picture: Vittorio Zunino Celotto/Getty Images

Still, if focusing on reducing your DAL means you increase your fruit and vegetable intake, it will bring health gains and help with numbers on the scales. “Plant-based foods, which are lower in protein and higher in potassium, such as fruits and vegetables, are a good place to start for increasing a diet’s alkalinity and reducing DAL,” Crowe says. There is no need to cut out animal foods completely, she adds.

It is about making sensible choices, Patel says, with moderate intakes of lean meats, such as turkey and chicken, and fish being better choices than fatty red meats and offal. With cheeses, the strong, aged varieties such as cheddar, parmesan and gruyere tend to have a higher DAL whereas ricotta and creamy cheeses are lower.

“I tend to focus on eating plenty of fruits and vegetables, many of which I try to consume raw without added salt or oil,” Crowe says. “But I also eat small amounts of lean animal proteins such as salmon as well as legumes, and beans, along with whole grains like brown rice.”

The bottom line, Patel says, is that consuming more plant foods is clearly good for our health and waistlines. “Whether the benefits are down to their alkalinity or their health-promoting nutrients,” she says, “we should all be eating more pulses, fruits and vegetables.”

This article originally appeared on The Times.