Start With a Vet Visit, Not a Smaller Scoop
Before food changes, an overweight senior needs examining. Extra pounds in an old dog can be partly condition and partly cause: an underactive thyroid adds weight, arthritis reduces the exercise that kept weight off, and some medicines and illnesses change appetite and metabolism. A vet can score his body condition honestly, check for those contributors, and set a target weight and a safe rate of loss, which for most senior dogs means slow, steady reduction measured over months.
Ask for his daily food amount in grams rather than cups. Scoops vary wildly between hands and households, and a level scoop heaped by a fond grandparent can quietly cancel a careful diet in a single weekend.
Weigh Meals and Put Treats Inside the Budget
Weighing every meal on a kitchen scale takes a week to become habit and removes the largest source of error in most home diets. Treats, chews, dental sticks, the corner of toast and the training rewards all count; either reserve part of his weighed daily food to use as treats, or reduce the bowl to make room for the extras he genuinely loves. A senior dog on a diet should never feel the household's affection has been withdrawn along with the calories, so swap food rewards partly for praise, grooming and short games.
Feed him separately if other pets eat freely, since a hungry dieter will hoover a housemate's leftovers with impressive speed and no remorse. Puzzle feeders and scattering part of his ration in the garden slow his eating and give him occupation that is not measured in calories.
Move More, in Pieces His Joints Approve
Exercise for a fat senior dog is built from frequency, not heroics. Four short walks on soft, flat ground usually serve stiff joints better than one long weekend march that leaves him sore until Tuesday. Sniff-heavy routes are valuable exercise for an old dog even at a stroll, and gentle slopes can be added gradually as fitness improves, watching his recovery the following morning as the true measure of whether yesterday was too much.
Swimming and hydrotherapy suit some arthritic dogs well because water carries the weight his joints cannot, but introduce water carefully and only where entry and exit are ramped rather than stepped. Stop and shorten future sessions if he lags, pants heavily, limps afterwards, or is reluctant to go out the next day; soreness is information, not stubbornness.
Weigh In Regularly and Adjust Patiently
Weigh him every two to four weeks, ideally on the same scales at the vet practice or a pet shop, and write the number down with the date. Home bathroom scales with a hold-the-dog subtraction are too rough to show the small changes that tell you a senior plan is working. If weight stalls for two consecutive checks despite honest measuring, take the food diary back to the vet rather than cutting portions on your own, because older dogs have less margin for nutritional shortcuts.
Expect plateaus and do not chase them with sudden reductions. Muscle matters enormously in a senior dog, since it gets him up from his bed, and a plan that preserves it beats a faster plan that strips it.
Protect the Progress From Household Drift
Diets fail at the edges: the second feeder who did not know he had eaten, the grandchild briefed by nobody, the neighbour's daily biscuit through the fence. Put his daily ration in a labelled container each morning so anyone can see what is left, and make the rule visible on the fridge until it is second nature.
Recording weigh-ins, ration changes and vet targets in KinsLe Pet Passport keeps the whole weight story in one portable packet, so any vet or helper sees the plan and its progress at a glance.