Appetite Loss
Do check with your vet in case this is due to illness. It's very common, however, for healthy young dogs to go through phases when they don't eat well, especially adolescent dogs, and all dogs when it's very hot. Entire lovesick males often go off their food. It usually does the dog no harm to miss a meal now and then. Obesity is a greater health risk than a dog being a bit underweight. Dogs also vary in terms of how much food they need, and yours may not conform to the advice printed on packs about how much a dog of his weight should eat. Go by your dog's condition and appearance, is he tired? Does he appear thin? Ask a vet if you aren't sure.
The timing of meals affects appetite, for example, feeding after rather than before a walk tends to mean dogs are hungrier at meal time. You can try leaving food down all day, noting when your dog eats, and then feeding at the times when his biorhythms tell him to eat. Dogs that don't want to eat at mealtimes may eat complete dried food presented to them as titbits when they are out on walks - good for reinforcing recall! Other tricks include boiling up a few leftover bones from your meals and pouring the flavoured water onto your dog's meal, and mashing it in. Try mixing in a little canned food, or boiled meat, if you normally use dry food. Don't give big meals if your dog won't eat them, so as to avoid waste. You can always give another small meal straight after if the first one is eaten.
Many dogs like to eat alone or they feel stressed, so it can be counter-productive to hover round a dog's bowl and fuss him. Some people become convinced the dog won't eat dog food and end up feeding him human food. Not all human food is good for dogs. Cook him special meals if you want to and have time. It's not really necessary just to get him to eat, though there are benefits to home-cooked food, if you research canine nutrition first. If there's nothing wrong with the dog, it's usually best just to relax and just try making the dog food more appetising. These phases usually only last a short while in healthy dogs.