The people of Tonga, by and large, are fat. They are proud to be fat. They want to stay fat. If they aren't fat enough by Tongan standards, they want to get fatter.

"The Complete Book of Running" wouldn't make the best-seller list in Tonga. The only joggers here are members of America's Peace Corps. They pant through the dusty, dilapidated capital of this pinprick in Polynesia while bulky Tongans, sitting under parasols on garssy patches, follow them with uncomprehending stares.

In America, it seems, fat people are carrying less and less weight. As Washington columnist Daniel S. Greenberg recently observed: "Perhaps the one basic agreement in this highly contentious society is that thin is better." He added flatly: "No fat man can be elected president of the United States."

In Tonga, the reverse is ture. There are skinny people, but they don't belong to the In Crowd. (Most fashionable amont them are the prostitutes and transvetites who dance with tourists and sailors at Joe's Hotel.) Here, as on other Pacific Islands, the fat cats and the big shots are big and fat.

Tonga's biggest man is His Majesty King Taufa'ahau Tupou IV, who rules the 169 mostly uninhabited islands and 100,000 citizens of this former British protectorate from the royal seat in Nuku'alofa. The king lives in a white, wooden palace that recalls a fairry Saratoga Springs hotel, and rides around in a 1950s-vintage black Cadillac with fins. He strains the scales at 380 pounds, affording him an unchallenged place in the "Guinness Book of World Records" as the world's weightiest monarch.

His Majesty is fat for historical reasons. Since 1845, he and his ancestors have owned every inch of Tonga's 258 square miles. Traditionally, the land is alloted to 33 nobles who assign 8 1/4 acres to every male commoner. The commoners raise food and donate the best of it to the nobles, who then donate the best of their food to the king. This is known as feudalism. It means the king gets an awful lot to eat.

Tonga's monarchs, consequently, usually have been monumental. Emulating royalty, ordinary Tongans aspire to adiposity as well. Thus, what is beautiful here might be considered somewhat beastly in the world of running. (A Japanese research team found last year that the average man on one Tongan island was 5 feet, 9 inches tall and weighed 180 punds, while the average woman was 5 feet 4 inches and 163 pounds.)

As far back as 1902, when even Europeans were on the plump side, a visiting Englishman came away with his impression of female loveliness in Tonga:

"The perfect woman must be fat -- that is most imperative -- and her neck must be short; she must have no waist, and if nature has crushed her with that defect she must disguise it with draperies, or submit to being 'miscalled' in the streets of Nuku'alofa, her bust, hips and thighs must be colossal. The woman who possesses all these perfections will be esteemed chieflike and elegant...."

Fashions change. Men still seek the shape and density of a medicine ball (the king is promoting sumo wrestling as the national sport), but women have come to prefer the bowling pin over the tree trunk. Long dresses emphasize stout midriffs and conceal the most alluring of female attributes: wide feet, nicely set toes, and the calf muscles of a linebacker.

The Tongan word for it is sino le le , which translates roughly as "healthy fullness." "Iths being well proportioned," says a young Tongan woman named Tupo, who considers herself too thin. "Your arms have to be thick enough. Your body has to be chunky enough. You have to have a certain amount of firm fat. Good eating will do it for you."

Some Tongans probably do eat strictly because they want to get fat. But at least as many, probably, get fat because they want to eat. "We don't like thin people, but we aren't really in love with fat," says Togan anthropologist 'Epeli Hau'ofa. "It's food that is admired. We just can't stop eating."

A variety of ponderous tubers is certainly at the root of the Tongan physique. In Nuku'alofa's outdoor market, where the air is scented by ripening bananas, logs of taro with the girths of good-sized flagpoles are on sale. Sweet potatoes come in convenient 40-pound baskets. Tongans lug them to the nearby bus depot with arms extended for balance.

The pride of Tonga's produce is the yam, a gnarled tuber with a dense white flesh that reminds a Western palate of damp wall-board. Yams sell in the market for $4 apiece. In a cullture that doesn't have much in the way of material things, people here show respect by giving them as presents. "It isn't only our chiefs who have diving origin," says Futa Helu, a Tongan educator."Our yams also are divine."

Meat traditionally is eaten in Tonga only on special occasions. For an out-of-the-way place, though, special occasions occur here with surprising frequency. Almost every church (Tongans are exuberant Christians) honors its preacher on Sunday with a numble offering of several roast suckling pigs. When an official visits a village, he gets the same treatment.

And when something really important happens, the government throws a gargantuan national feast on the king's front lawn. There have been three of these of late: on the king's 60th birthday, on the 100th anniversary of a friendship treaty with Germany, and when the Queen of England sailed in on the royal yacht during her jubilee tour.

For every national feast, Tonga's 35-biggest towns and its 33 nobles combine to serve up over 200 polas -- woven-palm stretchers 4-feet wide and 14-feet long piled with food to a depth of 2 1/2 feet. Each carries 25 pigs, 30 chickens, dozens of crayfish and heaps of vegetables. Guests sit on the ground and tear into the food with their hands. There is no talking. It is impolite in Tonga to talk while eating.

(An amateur photographer took a picture of Queen Elizabeth at her feast. With a decidedly queasy look she was eyeing a pig -- which seemed to be eyeing her back -- while the king, looming next to her, surveyed the pola with an eager grin. The queen graciously declined Tonga's hospitality and had her own food brought in from the yacht.)

Until recently, routine Tongan gluttony had produced a singularly healthy grade of flab. Because they got plenty of exercise and consumed only the odd pig, islanders were almost totally free of the diseases that help give fat its bad name in the West. Whole-some innocence, however, ended with the arrival of junk food.

Tongans now savor greasy mutton flaps from New Zealand almost at srdently as they do their yams. Food stores are laden with Krunchi Krisps, Big Cheese Cheesums, and Flovkies Bubble Gum. Two newly opened snack bars shovel out pretzels, popcorn and ice-cream sandwiches.

Public health doctors say they are beginning to come across cases of diabetes and high blood pressure. The king himself, who is reputed to be hooked on Coca-Cola, suffered a mild heart attack two years ago. He was ordered to shed 60 pounds, and subsequently got his weight down to 380 from 440. The Tonga Chronicle congratulated His Majesty on the achievement, nothing that "weight reduction among people with high social status is not an easy task."

But after a few hundred years of being fat and happy, Tongans aren't about to begin fretting like Westerners over a few extra pounds. "You complain that people will drop dead at 65 from being obese," a Tongan social worker lectured a New Zealand medical seminar last year. "Why not drop dead at 65 from being obese? Why not drop dead at 65? You've served your time."

There is no way around it -- fat is fashionable in Tonga. The kingdom has rejected jogging and absorbed salted peanuts. It complicates things for Dr. Laumeesie Maloro, a health-education officer marking the first tentative attempt to convince Tongans that they ought to lose weight.

"They tend to forget," he says of his dieting patients. "They don't follow instructions." Still, Dr. Maloro points out that there is one things a Tongan health officer can be grateful for: Nobody in these balmy islands is likely to die of starvation.