Many vets tell people with fat dogs to "reduce the amount you're feeding." This is bad advice because it will result in significant nutrient deficiencies.
AAFCO-compliant foods are formulated for K factors of 130. Most American dogs are fed at the rate of K factors 85- 95. This means that most dogs are not consuming even NRC and AAFCO minimums for most minerals and vitamins.
Example: 35-pound dog.
NRC / FEDIAF standards are 1.27 mg Mn for a 35-pound dog per day, (0.16 mg/kg(3/4))
If fed at an AAFCO K factor of 130, a food formulated to reach AAFCO Mn minimums will provide 1.27 mg Mn.
But when fed at the 95 K rate, which may be typical for adult dogs, the dog will consume only 0.94 mg Mn. 74% of recommended minimums.
NRC / FEDIAF minimum is 0.16 g Mg per day for a 35-pound dog. If fed at a 130 K factor rate, the dog will consume 0.16 g of Mg.
But if fed at 85 K factor, typical for lazy American dogs, the dog will only consume 0.1 g, or 65% of minimum recommendations.