As pet experts, we know that a dog’s dietary needs can change over time due to factors like their life stage or their activity level for example. Sometimes, it can be hard to tell if it’s time to switch up your dog’s diet, but there’s a few simple signs to look out for, including: Dull flaky coat Lethargy/weakness Sudden or rapid weight gain Upset stomach (chronic flatulence, loose stool or rumbly tummies) Stubborn itches