Sit by your dog when he’s lying on the floor, and make sure that you’re at his level as much as possible. Now check his abdomen, the part behind the rib cage. This part should be a little tucked up, meaning higher than the rib cage’s bottom.
To check more properly, run your hand alongside the rib cage toward the abdomen. If your hand starts curing to the dog’s back, they have the tuck and are therefore at a healthy weight. If your hand keeps going straight, your dog is probably facing obesity.
It may help to run one hand (palm side up) along the bottom of his rib cage towards his abdomen—if your hand curves up towards your dog’s back, then he has an abdominal tuck. If your hand goes in a straight line, he has no tuck and is likely obese.