Fat loss in cats runs on a calendar, not on willpower. A 12-week plan aiming at 0.5-1% of body weight per week, tracked in 4 records, takes most overweight cats to a 5-10% loss without the muscle wasting that crash diets cause. It also avoids the real danger: a cat that stops eating for 2-3 days can develop hepatic lipidosis inside a week. Weigh weekly, adjust every 14 days, and stop if loss passes 2% in 7 days.
Turn the cat into 4 baseline numbers
Before touching the food bowl, write down 4 numbers: weight in grams, body condition score (BCS, 1-9, target 5), rib coverage (0-3, where 0 means ribs are buried and 3 means they are sharp), and the waist tuck seen from above. A 6.0 kg cat at BCS 8 carries roughly 15-20% excess, so its target weight sits at 4.8-5.4 kg. Weigh on a baby scale to the nearest 10 g, same time of day, before the first meal and after the litter box. A 100 g overnight swing is water and gut content, not fat.
Do the calorie math once, then stop guessing
Resting energy requirement (RER) is 70 x body weight in kg to the power 0.75. At 6.0 kg that is 70 x 3.83 = 268 kcal. Maintenance for a neutered indoor cat runs about 1.2 x RER, so 320 kcal. A loss diet starts at 80% of maintenance: 255 kcal, or 20% below current intake. Convert to food weight: dry food at 350 kcal per 100 g gives 25-29 g, canned food at 80 kcal per 100 g gives 190-210 g. Mixed feeding is easier to control, because 200 g wet plus 25 g dry lands near 255 kcal. Hold protein at 35-40% of dry matter so the cat burns fat and keeps muscle.
The 0.5-1% weekly rule
Percentages beat fixed grams because the target moves as the cat shrinks. For a 6.0 kg cat, 0.5-1% is 30-60 g per week, or 4-9 g per day. At that pace the 12-week total is 500-600 g, an 8-10% loss. Faster is worse: a loss above 1.5% per week in a cat eating under 60% of its ration is the classic setup for hepatic lipidosis, and rapid loss takes 20-30% of the lost weight from lean mass.
Four records, one page, every Sunday
Record 1 is weight in grams. Record 2 is food actually eaten, weighed in grams on a kitchen scale, because a scoop varies 15-25% between two people. Record 3 is BCS plus a top-down photo every 14 days, since the scale hides body recomposition. Record 4 is a 0-3 daily score for appetite, play minutes, vomiting and stool. Four lines a week works; a 30-column spreadsheet dies by week 2.
The 12-week table
The plan below assumes a 6.0 kg cat at BCS 8, a 255 kcal starting ceiling, and mixed feeding at 80 kcal per 100 g wet, 350 kcal per 100 g dry. Treat the numbers as a template, not a prescription.
| Week | Target weight (kg) | Total loss (g) | Daily kcal | Wet g + dry g | Play (min/day) |
|---|---|---|---|---|---|
| 0 | 6.00 | 0 | 320 | 250 + 34 | 10 |
| 1-2 | 5.95-5.90 | 50-100 | 256 | 230 + 28 | 15 |
| 3-4 | 5.90-5.80 | 100-200 | 250 | 220 + 26 | 15 |
| 5-6 | 5.80-5.70 | 200-300 | 245 | 210 + 25 | 20 |
| 7-8 | 5.70-5.60 | 300-400 | 240 | 200 + 23 | 20 |
| 9-10 | 5.60-5.50 | 400-500 | 235 | 195 + 21 | 25 |
| 11-12 | 5.50-5.40 | 500-600 | 230 | 190 + 20 | 25 |
Weeks 1-2: measure before you cut
Feed the current ration for 7 days and log every gram. Most owners discover the cat eats 15-30% more than they estimated, and the first fix is portioning, not a new diet. Weigh twice in week 1 to learn how noisy your scale is. No calorie cut yet.
Weeks 3-8: the steady middle
Cut 10% of calories every 14 days only while weekly loss stays under 0.5%. If loss runs 0.5-1%, change nothing. If it passes 1.5%, add back 10% and recheck in 7 days. Split the ration into 4-6 meals, since 2 large meals drive begging and 3 a.m. wake-ups. Add 10-15 minutes of play 2-3 times a day; a session burns 5-10 kcal, which is small, but it protects lean mass and cuts the pacing that owners read as hunger. A trend chart helps more than a single number, and the method is laid out in reading a weight trend chart.
Weeks 9-12: taper, then hold
The last 3 weeks are for landing, not sprinting. When the cat reaches 5.4 kg or BCS 5, stop cutting and feed maintenance for 4 weeks: about 1.0-1.1 x RER at the new weight, so 210-230 kcal. Weigh at weeks 13 and 16. A regain of more than 100 g in 2 weeks means the ceiling was too low and the cat is compensating between meals.
When the scale stalls for 14 days
Recalculate RER at the current weight first. A 0.5 kg drop lowers RER by 15-20 kcal, and an unchanged ration slowly becomes maintenance. Then audit the 4 records for hidden intake: treats (a 5 g treat is 15-20 kcal), licking the dog bowl, 2-3 kibble stolen per day. If intake is honest and loss is flat for 21 days, ask the vet about thyroid and diabetes testing before cutting further.
Two cats, one bowl problem
In a 2-cat house the diet usually fails at the bowl, not at the math. Feed in 2 separate rooms, close the door for 20 minutes, and pick up what is left after 30 minutes. A second cat eating 15 g of the diet cat's food adds 50 kcal a day, which erases a 20% deficit in 3 days. If one cat is thin and one is heavy, feed the thin one 20% above its own RER and use a microchip feeder.
Stop the plan and call the vet
End the diet and book a visit for any of these: more than 2% loss in 7 days, no food for 24 hours, intake under 50% for 3 days, yellow gums or ear pinnae, vomiting 2 or more times a week, or hiding and weakness. A cat that stops eating for 2-3 days needs calories from a vet, not a stricter diet. Background on the medical side is in obesity and weight loss.
Five moves for this week
- Weigh the cat tonight, before dinner, and write the grams down.
- Weigh 3 days of food to find the real intake.
- Set the ceiling at 80% of maintenance, never 50%.
- Put a 14-day recheck on the calendar, not in your head.
- Photograph the waist from above and repeat every 14 days.
Terms mentioned in this article
Frequently asked
How fast can a cat safely lose weight?
Aim for 0.5-1% of body weight per week, which is 30-60 g for a 6 kg cat. Loss above 1.5% per week raises the risk of hepatic lipidosis and costs lean mass, so slow the plan down rather than pushing harder.
What if my cat begs between meals on a diet?
Split the daily ration into 4-6 small meals, use a puzzle feeder for 1-2 of them, and add 10-15 minutes of play before the largest meal. Begging usually tracks meal size and timing, not true hunger.
When should I stop dieting and see a vet?
Stop if the cat loses more than 2% in 7 days, refuses food for 24 hours, eats under half its ration for 3 days, shows yellow gums, or vomits twice a week. These point to liver or metabolic trouble, not a stalled diet.