The fact that probably 80% of modern dog trainers use food, no matter what other tools they are using (or not - remember, I train as naked as possible), doesn't seem to have filtered into 1) marketing materials that inform potential clients and 2) the general population. There are many people who still tell me they don't want to use food to train their dogs and they have just as many reasons why not.
1) A dog trained with food won't do the behaviors without the food
2) The dog will get fat
3) My dog isn't food motivated
4) Behaviors trained with food are unreliable
5) My breed needs a heavy hand
6) My dog should do it just because I ask
7) Food won't keep my dog from biting another dog/person
And many more reasons why food isn't good.
What I have seen with many who do use food in the training process is a total misunderstanding of the role of food in training and in life.
Food is used in many ways.
1) It is used as a lure. I.E. to motivate a dog to want to follow the food in a special way so as to be able to eat the food when that movement is done.
2) It is used as a reward for a successful movement, movement that the trainer either is teaching or asking for with a cue/command. If the dog does the movement, and does it correctly, they get food. The food is usually visible or understood to come out of a specific pouch or pocket.
These first two methods have been said to "bribe" the dog into acting as requested.
What is a bribe?vb
1. to promise, offer, or give something, usually money, to (a person) to procure services or gain influence, esp. illegally
2. a reward, such as money or favor, given or offered for this purpose
3. any persuasion or lure
3) As reinforcement which is different from a reward in that reinforcement is more of a consequence then a lure.
Reinforcement is appropriate to the behavior as a consequence, not an added extra. It could still be argued that it is a bribe, that the anticipation of reinforcement is still a motivator for behavior. But I ask you, is there any consequence that doesn't motivate? Motivation isn't always on the "good" side, there are motivators that also prevent the "bad". The seeking of pleasure/reinforcement/survival is a part of life, it pushes evolution and change. The avoidance of pain/death/avoidance is just as powerful if not more so and often creates single instance learning. These are the ultimate reinforcers, the ultimate in motivation.
Eating food is a consequence, but it is not where a creature gets it's pleasure, the final act is not where evolution has placed the most rewarding chemical changes in the body, nor where the spirit focuses. The pleasure is in the doing, the changing landscape of emotions and movement. All that stops once the goal is attained.
A true reinforcement is an event in itself, heightening the pleasure, prolonging it. A true reinforcer will cement the need to move and emote in that same way again and again. Food doesn't qualify.
4) As a distraction
Anything your dog desires is a distraction to her doing as asked or learning something new. Any conditioned or learned or instinctive antecedent is also a distraction to learning. An antecedent is a trigger for movement to happen in order to gain reinforcement. If that trigger is stronger then the reward/lure/bribe you are offering, it's a distraction. Or as well known sports training Michael Ellis calls "a competing motivator".
The way things are
Having said that, which would you rather do for the life of your dog?
Punishing/creating avoidance from time to time? or using reinforcing methods? You can't expect a dog, anymore then a human could, to remember how to do things learned a year ago without actually maintaining them somehow. Obviously maintaining what they've learned is a whole lot easier then teaching them, but it still has to be done - for the life of the dog.
So whether you are set on using food in it's various ways to train or have other tools in your arsenal, you must be prepared to use those tools at intervals or the training you did, the behavior that you modified or changed, will fade and eventually pass out of use.