Obesity does not only put individuals at risk for heart disease and diabetes—it's also a leading cause of kidney stone disease.
Kidney stone disease is increasingly recognized as a chronic condition closely tied to metabolic health, with obesity standing out as a major risk factor. Conditions such as diabetes, hypertension, and cardiovascular disease are also closely associated with the development and recurrence of kidney stones.
This shift in perspective is essential for addressing kidney stones as part of a larger health challenge, emphasizing the importance of long-term prevention strategies., including lifestyle changes and medical interventions.
Kyle Wood, M.D., associate professor in the UAB Department of Urology, discusses the link between obesity and kidney stones, ongoing research, and potential treatments.
Kidney stone disease is a chronic condition
Kidney stone disease is revealing itself as a chronic condition closely linked to metabolic health.
"Many things are linked to kidney stone disease," Wood explained. "I think we really need to think of kidney stone disease as a chronic disease."
This change in perspective is crucial. Traditionally, kidney stones were regarded as singular events rather than symptoms of an ongoing metabolic imbalance.
"Once we shift the mindset of practitioners and health care providers to really think of kidney stones less as an episodic issue, but more as a chronic issue, then we'll be able to start tackling it as a chronic disease,” Wood said.
Obesity increases kidney stone risk
Obesity is a metabolic disorder that not only increases the risk of various health problems such as heart disease, diabetes, and hypertension, but it is also a significant risk factor for kidney stones.
"With obesity, there's an increase in usually two types of stones," Wood explained. "There's an increase in both calcium oxalate stones and uric acid stones."
The formation of uric acid stones is strongly linked to insulin resistance—a hallmark of obesity and diabetes.
"As insulin resistance develops, it alters urine composition," Wood said. "One key change is a drop in urine pH, making it more acidic. This acidic environment promotes uric acid stone formation."
Calcium oxalate stones also occur more frequently in obese individuals, though the mechanism is multifaceted.
"It raises the question: Why does obesity increase kidney stone risk?" Wood said. "We know that as body mass index (BMI) and waist circumference increase, urinary oxalate excretion also rises."
To better understand this connection, collaborative research with the UAB Nutrition and Obesity Research Center (NORC) and the Kidney Stone Research Lab suggests that excess oxalate comes from both dietary sources and the body’s own production.
Through an NIH grant, Wood and Goss examined the role of BMI and oxalate levels, finding that as BMII increases, so does the production of oxalate, offering a potential explanation for the link between obesity and kidney stones.
"We've investigated whether high-oxalate foods are responsible or if the body is generating more oxalate internally," Wood said. "Our findings suggest that obesity influences both factors."
Treatments
The connection between obesity and kidney stone disease highlights the importance of addressing both surgical and medical treatments in managing this condition. Kidney stone treatment generally falls into two categories: surgical intervention and medical management. Surgical procedures aim to physically remove kidney stones, particularly in acute cases. Medical management focuses on reducing the risk of stone recurrence, often through lifestyle modifications and medications.
Ongoing research: fatty liver disease and kidney stones
One of the newest areas of research is the connection between fatty liver disease—now referred to as metabolic-associated steatotic liver disease (MASLD)—and kidney stone formation.
“We’re pioneering research that links fatty liver disease to kidney stones,” Wood said. “Oxalate, a key component in many kidney stones, originates in the liver, which means metabolic disturbances in the liver could influence stone formation.”
Since obesity increases the likelihood of developing MASLD, this condition may be a missing link in understanding why obese individuals have a heightened risk of kidney stones. Rather than obesity alone being the primary factor, it may be the underlying metabolic dysfunction, such as fatty liver disease, that plays a key role.
This hypothesis led to a recent R03 NIH grant awarded to Wood and Goss to evaluate the role of MASLD in oxalate production. Given that oxalate originates in the liver, their research is exploring how liver-related diseases like MASLD may alter oxalate levels and contribute to stone formation.
Understanding the link between obesity, fatty liver disease, and kidney stones provides a new perspective on prevention and treatment. Addressing obesity as a root cause—through weight management, dietary changes, and metabolic research—could lead to better strategies for reducing kidney stone risk in the future.