What do Xu Zhipeng and Rick Bumgardener have in common?

Zhipeng, 23, a computer graphic designer in Shanghai, is 6-foot-2 and weighs 157 pounds. Bumgardener, 54, of Halls, Tenn., is a retired school-bus driver who's trying to shed 100 pounds so he'll be eligible for weight-loss surgery. At 5-foot-9, he weighs 468 pounds.

Each man eats about 1,600 calories a day.

Both are featured in the recently published book "What I Eat: Around the World in 80 Diets" (Material World), which documents in text by Faith D'Aluisio and photos by Peter Menzel the way 80 people from 30 countries eat. All the information I report here, including subjects' ages, is as it appears in the book. It's a gorgeous volume and, at 4 pounds 3 ounces by my kitchen scale, a weighty one.

I read an awful lot about nutrition and food, but never before have I seen such a broad and graphic demonstration of what real people put in their mouths. The book also drives home how directly our cultures and lifestyles are intertwined with the way we eat.

This latest book from Menzel and D'Aluisio (the California husband-and-wife team that gave us "Hungry Planet" in 2005) is organized according to the number of calories each of its subjects consumes in a given day. This became a useful lens through which to view menus that differ so markedly from one another, and from my own comparatively boring daily regimen. And it allows the authors a framework for introducing their subjects with respect and without judgment.

"What I Eat" presents a baffling array of body types, foodstuffs and dining habits. It begins with a profile of Noolkisaruni Tarakuai, a 5-foot-5 Maasai cattle herder in Kenya who, at age 38, weighs 103 pounds and ate only 800 calories on her depicted day. It ends with 31-year-old Jill McTighe of Willesden in northwest London, who is represented by a binge day that tallied an astounding 12,300 calories. McTighe, whose eating habits result in part from her past struggle with amphetamine abuse, is also 5-foot-5, but she weighs 230 pounds.

How to make sense of the disparities? For one thing, the calories listed are snapshots of a single day and may not be sustainable long-term. Beyond that, Menzel told me, "Most of the world is driven by economics. The choices they make are based on what they can afford. In the developing world, diets are grain-based, with less meat. That's a generally healthier way of eating."

But, he continues, "With more wealth, people add more things. . . . Sweets, fats, meat, milk. When people have more money, that's what they go for."

Extremes aside, the bulk of participants' calorie counts cluster closer to 2,000, the standard number on which U.S. federal dietary guidelines are based and around which Nutrition Facts panels are built.

And that's as it should be, suggests Susan Roberts, senior scientist and director of the Energy Metabolism Laboratory at Tufts University. Roberts hasn't read "What I Eat," but she gets the gist and is concerned that the extreme cases it presents might skew people's views of how many calories they need. Roberts says U.S. dietary guidelines take into account such factors as gender, age, height and activity level in assigning optimal calorie intakes, which generally range from 1,600 calories to 3,000 a day.

Roberts says that unless you're trying to lose or gain pounds, energy (or calorie) intake should equal energy expenditure.

In "What I Eat," that equation is not always clearly in play. Take Jeff Devine, a 39-year-old high-rise ironworker in Chicago, who is photographed on a beam 50 stories up, his day's repast spread before him. Except for a banana, it's all packaged, processed food, but mostly healthful stuff such as smoked salmon, cottage cheese and a fruit cup. Devine's spread also includes 10 bottled beverages of various sizes; six of those are diet sodas, and just three of those are little 12-ouncers. (D'Aluisio says that after overhearing people commenting on the amount of soda in that photo, Devine cut back.)

According to the book, the 6-foot-1 Devine weighs a reasonable 235 pounds despite consuming some 6,600 calories a day. (Readers of last week's column will recall that even the biggest, beefiest NFL football player doesn't need more than 6,000 calories to fuel his practice and play in-season.) It's hard to fathom that Devine's food adds up to that many calories, especially with all those diet sodas. And it's hard to see how he can burn it all off, even with a job and bodybuilding regimen that demand lots of fuel. (The book doesn't attempt to calculate the calories people burn.)

Menzel and D'Aluisio make plain that they are not nutrition experts (though they've included in the 340-page book essays and commentaries from dozens of experts, many with helpful nutrition info), so they've taken pains to explain in detail their methods for collecting, analyzing and presenting data.

And, in the spirit of fairness or perhaps of self-discovery, Menzel and D'Aluisio reveal their own daily diets and calorie intakes in the afterword. His calories: 2,800 per day. Hers: 1,500. Their meals are, predictably enough, full of fresh fruits and vegetables, yogurt, granola, organic peanut butter, with just enough butter (plus a Tootsie Roll Pop) to humanize the pair. Menzel, 61, is 6-foot-1 and weighs 168 pounds. D'Aluisio, 52, is 5-foot-8 and weighs 135 pounds.

In other words, they're the picture of health.