By MICHAEL BARBARO


He dumps salt on almost everything, even saltine crackers. He devours burnt bacon and peanut butter sandwiches. He has a weakness for hot dogs, cheeseburgers and fried chicken, washing them down with a glass of merlot.

Mayor Michael R. Bloomberg has become New York City’s nutritional nag, banning the use of trans fats, forcing chain restaurants to post calorie counts and exhorting diners to consume less salt.

But an examination of what enters the mayoral mouth reveals that Mr. Bloomberg is an omnivore with his own glaring indulgences, many of them at odds with his own policies.

As a billionaire in one of the dining capitals of the world, he can eat anything he wants. But he is obsessed with his weight - so much so that the sight of an unflattering photo of himself can trigger weeks of intense dieting and crankiness, according to friends and aides.

His food issues have become New York City’s. Although he has described his battle against unhealthy foods as common-sense policy that will shed weight (and save lives), many of his targets overlap with his own cravings.

“I like a Big Mac like everybody else,” he confessed recently, explaining the city’s approach to fast food. “I just want to know how many calories are in it.”

Under his watch, the city has declared sodium an enemy, asking restaurants and food manufacturers to voluntarily cut the salt in their dishes by 20 percent or more, and encouraging diners to “shake the habit” by asking waiters for food without added salt. But Mr. Bloomberg, 67, likes his popcorn so salty that it burns others’ lips.

Friends of the mayor said that, like most New Yorkers overwhelmed with food choices, he swings between two dietary poles: indulgence and abstemiousness. After a dinner loaded with fat and salt, they said, he will consume a grapefruit for breakfast, then a bowl of soup for lunch.

The mayor’s press secretary, Stu Loeser, said Mr. Bloomberg “works as hard as any New Yorker at keeping off extra pounds, and he has trimmed himself down to his college weight, which isn’t at all easy for a 67-year-old.” The mayor, he said “has days when he eats more than he should.” But, he added, “unlike most of us, he has the discipline to even it out the next day.”

As for his apparent policy of salt as I say, not as I do? Friends note that the mayor smoked cigarettes for years before he banned the practice in restaurants across the city, and besides, it’s the salt in processed foods, not in shakers, that poses the greatest health risk.

For New York City’s richest man, his table manners are surprisingly relaxed: he is known to grab food off the plates of aides and, occasionally, even strangers. (“Delicious,” he declared recently, after swiping a piece of fried calamari from an unsuspecting diner in Staten Island.)

Still, he hates to be fussed over, no matter how much the meal costs. One dinner companion recalled that after Mr. Bloomberg asked for the best bottle of red wine in the house, the restaurant’s manager wanted to describe the wine to the mayor, have him taste it and smell the cork.

The mayor politely interrupted. “Is this your best bottle?” he asked. The manager said yes. “O.K., then pour it,” he said.

ROBERT GROSSMAN