First published in 2019. Rewritten in October 2026 to reflect current evidence and add safety guidance.
Intermittent fasting means leaving longer breaks between meals. It has become popular for people, and many owners ask whether it could help their dog. The honest answer: it may help some healthy adult dogs; the evidence in dogs is still early, and for some dogs it is not safe at all.
Please talk to your veterinarian first. Do not fast your dog or cut back their food without your veterinarian's agreement if your dog:
- has diabetes or is on insulin, as skipped meals can drop blood sugar dangerously
- has an insulinoma or a history of low blood sugar
- has cancer and is losing weight or appetite
- is underweight, frail, or recovering from illness or surgery
- is a puppy, a toy or small breed, or pregnant or nursing
- is a large, deep-chested breed at risk of bloat, as one large meal a day can raise the risk
- vomits yellow bile when their stomach is empty
Always leave fresh water out, whatever the feeding schedule.
When a sick dog stops eating
Dogs who feel unwell often go off their food. It can be tempting to see this as the body resting, but a dog who stops eating, or loses weight without trying, needs a call to your veterinarian. This matters most for dogs with cancer, where keeping weight and strength is a big part of having good days.
What the research says
Staying lean. The strongest evidence is about body weight, not meal timing. In a lifetime study of Labrador Retrievers, dogs kept lean lived longer, and showed signs of chronic disease such as arthritis later, than littermates who were fed more (Kealy and colleagues, Journal of the American Veterinary Medical Association, 2002). Lean means a healthy weight, not thin.
Meal timing. The Dog Aging Project compared dogs fed once a day with dogs fed more often, using information from owners of thousands of companion dogs. Dogs fed once a day scored better on several health measures. But the study shows a link, not a cause, and the researchers say it should not be used to decide how often to feed your dog. Read the Dog Aging Project's summary.
You may read that fasting "detoxifies" the body. There is no good evidence for this in dogs.
If your veterinarian agrees
For a healthy adult dog at