The best way to know if your whippet is overweight is by looking at their ribs. If you cannot see any ribs, it means that they are overweight. Along similar lines, if you can see more than three ribs, it means they are underweight and undernourished. Additionally, their appetite and behavior are other aspects to consider. A dog that is lethargic or is otherwise disinterested in food could indicate they are in an overfed state.