Treat Obesity in Pets to Improve Liver Health

Written By Dr. Ernie Ward

What we’ve long suspected is now official: the FDA just approved a weight-loss drug to treat liver disease.

On August 15, 2025, the US Food and Drug Administration (FDA) granted accelerated approval for semaglutide (Wegovy®) to treat metabolic dysfunction-associated steatohepatitis (MASH) with moderate to advanced fibrosis in adults (FDA, 2025). That decision does more than add another indication for a familiar drug. It reframes obesity therapy as liver therapy, raising a practical question for veterinary teams and the industry: if treating obesity improves liver outcomes in humans, how should we monitor and communicate liver outcomes in dogs and cats? 

Two human health trends make this especially relevant to the veterinary profession.

First, liver nomenclature has shifted from NAFLD/NASH to MASLD/MASH, with the new terms highlighting the role of metabolic dysfunction. In practice, this better reflects the biology we already explain to colleagues and clients about how excess fat and weight impact the liver (Rinella et al., 2023).

Quick review: NAFLD/NASH (nonalcoholic fatty liver disease and steatohepatitis) are now MASLD/MASH (metabolic dysfunction–associated steatotic liver disease and steatohepatitis). MASH is the more serious form, carrying risks such as cirrhosis and liver cancer.

Second, large human datasets now connect modern obesity pharmacotherapy to broader disease prevention signals, including cancer risk reductions with GLP-1 receptor agonists (Dai et al., 2025). That evidence base does not transfer wholesale to animals, but it strengthens the concept that effective obesity treatment can modify organ-level outcomes. 

So what does the evidence tell us about the connection between obesity and liver dysfunction in dogs and cats?

Cats

In cats, the connection between obesity and liver injury is fairly direct. Cats with obesity or “obesity-disease” feline phenotypes show higher ALT and inflammatory markers, signs consistent with active hepatic stress (Kobayashi et al., 2025). Feline hepatic lipidosis remains a classic obesity-adjacent emergency, and mechanistic reviews place obesity, insulin resistance, and negative energy balance at the center of this life-threatening disorder risk (Ling et al., 2025). 

Interestingly, emerging therapeutics that target metabolic signaling, such as activating the FGF-21 pathway, have been shown to produce weight loss in cats with obesity and suggest improved hepatic lipid handling (Brinker et al., 2023). 

Dogs

In dogs, the picture is more nuanced. A well-controlled sonographic hemodynamic study found that dogs with obesity had altered portal flow and higher cholestatic enzymes, particularly ALP and GGT, even when ALT was normal (Belotta et al., 2017). 

More recently, noninvasive tools borrowed from human hepatology are being applied in veterinary practice. Ultrasound attenuation imaging (ATI) can quantify liver fat in hyperlipidemic dogs and may become a useful monitoring metric during weight loss (Pelligra et al., 2024). 

Canine obesity is often accompanied by hepatobiliary stress, characterized by cholestatic enzyme changes, elevated ALP, and occasionally elevated GGT, and sometimes hepatic steatosis (fatty infiltration of the liver). Therefore, ALT alone is an inconsistent signal of obesity-related liver disease in dogs. 

Clinically, track ALT, ALP, and GGT in conjunction with fasting triglycerides and cholesterol, and, when indicated, add bile acids and hepatic ultrasound (including attenuation imaging when available) to screen for steatosis. Use ALT only in context, not in isolation.

What should veterinary teams and the industry do now?

1) Use the right language. 

Adopt the updated human terminology (MASLD/MASH) in your conversations with clients and colleagues. This framing connects obesity to liver health and helps reinforce why metabolic control matters. 

Align client education, CE, and product messaging with the new nomenclature, not outdated acronyms. An excellent start is to review Rinella’s “A multisociety Delphi consensus statement on new fatty liver disease nomenclature,” published in December 2023. (Rinella et al., 2023).

2) Monitor the right markers. 

Cats: Get a baseline liver panel (ALT, ALP, bilirubin) and consider serum amyloid A (SAA) to detect and track liver dysfunction and systemic inflammation during obesity treatment. Create a therapeutic diet plan that avoids fasting and recheck early (e.g., the first 2 to 4 weeks for BCS 8-9/9) to confirm adequate food intake and trend markers. Let’s work together to educate our veterinary colleagues on the utility of feline SAA in identifying and tracking systemic inflammation. (Kobayashi et al., 2025). 

Dogs: For dogs diagnosed with obesity, include ALT, ALP, GGT, and triglycerides to monitor liver function. Consider obtaining a quantitative imaging baseline (e.g., radiographs, ultrasound, CT/MRI) when possible. If ATI or elastography (an ultrasound or MRI technique that measures the “stiffness” or elasticity of body tissues to help diagnose and assess disease) is available locally, capture it before and after weight loss to document hepatic improvements (Pelligra et al., 2024). 

3) Track more than weight. 

Weight loss is a means, not the end. The goal is better body composition: reduce body fat while preserving or building lean mass to improve quality of life, lower disease risk, and extend healthy years.

Based on the latest research, include and track liver-specific endpoints in obesity care plans: liver enzymes, bile acids when indicated, and a practical imaging metric. Industry partners can help by standardizing simple obesity biomarkers, diagnostic panels, and reporting formats for weight-management programs.

4) Frame obesity treatment as organ protection. 

The human drug approval story is clear: reducing adiposity can modify liver pathology in a disease with transplant-level consequences (FDA, 2025). Liver health is part of the reason why we’ve been encouraging veterinarians to “treat obesity first” when caring for a dog or cat with obesity.

While veterinary approvals for GLP-1 RAs and other anti-obesity drugs are still in development, your therapeutic weight-loss diets, exercise and activity plans, and behavioral interventions are already helping to lower disease risk, including liver dysfunction, today. Say that out loud. Measure it. Publish it. 

5) Push the research forward. 

There’s a need for prospective weight-loss cohorts in dogs and cats. Priority studies include prospective weight-loss cohorts in dogs and cats with predefined hepatic endpoints, as well as pragmatic trials that pair clinic-ready imaging with routine biochemistry. If your hospital can contribute data, now is the time. Contact us at APOP or the World Pet Obesity Association (WPOA) to explore potential collaboration opportunities. 

The headline is simple: Human regulators have approved an obesity drug for treating a liver disease. Veterinary medicine should follow by sharpening how we explain the obesity-liver connection, how we monitor at the patient level, and how we measure success. Clients will understand the message, and their pets’ livers will benefit.

Key references to read

Dr. Ernie Ward https://www.DrErnieWard.com
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