I recently received an email on my radio show asking the following question: ''How come even old diet veterans have such a hard time staying on the healthy eating track?''

The writer went on to detail her own personal battles with food with certain situations being particularly problematic. For her, these situations included being on vacation, eating with her family and, especially, attending social events.

Her question is profoundly familiar to anyone who has ever struggled with weight. This was a person who had had great success with a particular diet, yet she kept falling off the wagon. And once she did, she found it difficult to get back on track. She wondered if I had any thoughts on the subject.

Sure I do. And one of them is this: I think it's darn near a miracle that it doesn't happen more often.

Here's why: There are powerful forces that can often seem to be conspiring to work against you when you try to change your eating behavior patterns.

Fortunately, understanding these forces can help lessen their power over you. Here are the top five reasons we stray from our diets and some thoughts on each of them:

1. Habits and Conditioning
Eating behavior becomes conditioned from the moment we're out of the womb. Food is strongly associated with all kinds of social situations, rituals, places, people and emotions -- not the least of which is comfort. Those responses don't just ''go away'' in a few weeks or even months. You might as well expect that there are going to be times when a particular constellation of those factors -- people, places, things and emotions -- will simply overwhelm even the best intentions.