Your dog is leaving food, and it turned cold at about the same time. Some dogs eat less in winter and some eat more, so the season alone tells you nothing. Three checks and a decision will.
Go to an emergency vet now if he's retching with nothing coming up, his belly looks swollen or tight, or he has collapsed or is struggling to breathe. If he's refusing whole meals, vomiting, or visibly losing weight, skip to "When to call the vet" at the end. What follows is for a dog who is still eating most meals and otherwise acts like himself.
1. Is he moving less?
Add up the minutes he spends outside on a normal day this week, then do the same for a day before it turned cold. Write both down. The drop is often bigger than it feels: the twenty-minute morning loop becomes five minutes at the curb, and the weekend walk doesn't happen.
Fewer walks means fewer calories burned. Some dogs eat a little less to match, and some keep eating the same and gain weight. My Alaskan Malamute sleeps flat out on the tile all summer; once it turns cold she stays in her bed far longer than she used to. Look at where your dog is lying right now.
A dog can also move less because moving hurts. Stiff for the first few minutes after getting up, slow on the stairs, reluctant to jump onto the couch, avoiding hard floors he used to like. In an older dog that is a vet visit, not a smaller portion.
If your dog spends hours outdoors in freezing, wet or windy weather, or sleeps somewhere unheated like a garage or on concrete, this flips. He may be burning more calories to keep warm, not fewer. His first need is a dry, draft-free place off the ground and water that isn't frozen, and a coat on cold walks if he is short-coated. Extra food comes second. The ASPCA's winter advice is to "feed your pet a little extra in the winter months," because pets burn extra energy staying warm. That fits a dog who is really cold. It doesn't fit a dog asleep on the couch, which is why you check first.
2. Is his weight changing?
- Weigh him today, on the same scale at the same time of day, and write it down. For a small dog, a baby scale or a free weigh-in at your vet's beats a bathroom scale.
- Feel his ribs today. You should find them easily under a thin layer, without pressing hard, and see a waist from above. If you can't find the ribs, he's carrying extra. If ribs, spine or hip bones stand out, he's too thin. A thick coat hides this, so let your hands decide.
- Weigh him again in two weeks. If he's eating less, weigh him every week.
A home scale wobbles by a couple of percent, so trust a trend across weigh-ins, not one reading. If he's eating less and the scale is already down at the first re-weigh, call your vet. Don't wait for the next one.
3. How much is he really leaving?
"He's eating less" is usually a feeling. Give him his normal amount for three days, in the same bowl, weighed on a kitchen scale if you can. After each meal, note what's left: finished, about half, barely touched.
Three days is long enough to catch a dog who is getting worse. It isn't long enough to prove he's fine. If the leftovers grow day by day, or he skips a meal, treat it as a health question. If they stay about the same, keep tracking until the second weigh-in.
Leaving a little is a different picture from refusing a whole meal. The first can be a dog matching a smaller day. The second isn't a seasonal pattern.
If he seems hungrier, track it the same way. Eagerness at the bowl tells you about his food drive, not how much he needs: a dog whose walk went from forty minutes to ten can still sprint to dinner and clear it in thirty seconds. And if your summers are hot, remember that heat can reduce appetite (VCA lists high environmental temperature among the causes), so he may have eaten less in July than he normally does. Compare with spring or fall.
4. What to do with the portion
Put the three answers together.
- Moving less, weight and ribs steady, leaving a little. Leave the amount alone.
- Moving less, weight up, cleaning the bowl. Cut the extras first, then trim his meals by a small step, around a tenth, and weigh again in two weeks. AAHA's guideline is to keep all extras to 10% or less of daily calories, and winter treats, chews and table scraps add up fast. Here's how to work out what 10% is for your dog. If you warm his food with broth, it counts too, and check the label: onion and garlic are toxic to dogs, powder included.
- Cold-exposed, cleaning the bowl, weight steady. No change. If his weight is slowly falling, add around a tenth to his meals and weigh again in two weeks. If he's leaving food or still losing at two weeks, don't add more. Call your vet.
- Weight and appetite pulling in odd directions. Gaining while eating the same or less, hungrier but losing, a bigger belly, more thirst or panting, a thinning coat. That is a vet question, not a portion question.
- Moving less, weight down. Book a vet visit this week.
- Refusing whole meals, or leftovers growing day by day. Go to "When to call the vet."
The tenths are our own cautious starting points, not a guideline. To see roughly how much he should be eating, use our calculator and treat the answer as a starting point, which is how Merck's manual describes any calorie formula.
Don't set the amount from the calendar in either direction. "It's December, add a scoop" and "put some weight on him before the cold" both skip the checks above. Body fat does insulate, but it loads the joints and takes months to shift, while a bed up off a cold floor works the same week.
Two situations this page doesn't cover. A puppy eating more is mostly growing, and a pregnant or nursing dog's needs climb steeply. Both are plans to make with your vet.
When to call the vet
These timings are our own cautious rule, not a guideline.
Emergency vet now:
- Retching or trying to vomit with nothing coming up, even if his belly looks normal. Or a belly that looks swollen or feels tight, especially with restlessness, heavy drooling or fast breathing. VCA describes these as signs of bloat (GDV), which is life-threatening, is most common in large, deep-chested dogs, can affect any dog, and needs treatment within minutes to a few hours
- Collapse, pale gums, wobbliness, trouble breathing, or a seizure
- Any chance he got into antifreeze, chocolate, xylitol, rat poison or human medication. Go now, or call the Pet Poison Helpline at (855) 764-7661 (a fee applies). Wipe his paws and belly after winter walks, because ice melts and antifreeze are dangerous if swallowed
Call your vet today:
- He skips a second meal in a row, or skips one and anything else is off: quiet, drinking oddly, an upset stomach
- Vomiting more than once, vomiting with lethargy, blood in vomit or stool, or drooling more than usual
- He goes to the bowl, starts, then backs off. Or chews on one side, drops food, paws at his mouth, or has bad breath that's new. Mouth pain is a common cause, and nausea can look the same
- He keeps shivering in a room that feels comfortable to you. Pain, nausea and fever are more likely causes than cold, though small, short-coated and older dogs do feel cold sooner, so warm him up and see if it stops
- You can see or feel weight coming off
Book a visit this week if he has been leaving half or more of most meals for more than three to five days, even though he's still eating something. Don't wait that long if he's a puppy, small, older, or has a known health condition such as diabetes, kidney disease or Addison's.
A dog who has eaten nothing for 24 hours needs to be seen. Some dogs have less room than that:
- A young puppy or toy-breed puppy who misses a meal or seems weak or wobbly: call right away
- A puppy, very small dog, or pregnant or nursing dog who skips a meal: same-day call
- A dog with diabetes who skips a meal: call before the next insulin dose, and don't give a full dose unless your vet has told you to
- Any dog who isn't drinking either: same-day call
How long a dog can safely go without food covers this in more detail. If he's an older dog, check four things in a senior first. If he's off his food but otherwise entirely himself, start with a dog who isn't eating but is acting normal.
Sources
- ASPCA, Cold Weather Safety Tips
- VCA Animal Hospitals, Anorexia in Dogs
- VCA Animal Hospitals, Bloat: Gastric Dilatation and Volvulus in Dogs
- American Animal Hospital Association, 2021 AAHA Nutrition and Weight Management Guidelines for Dogs and Cats
- Merck Veterinary Manual, Nutritional Requirements of Small Animals