March 12 (Bloomberg) -- Japanese waistlines are bulging, triggering compulsory flab checks in the land of sumo.

A rising rate of corpulence has so alarmed the government that starting next month everyone over age 40 will have to be tested for metabolic syndrome, an obesity-linked condition that increases the risk of heart disease and diabetes.

The exams have helped make the battle of the bulge a national obsession. Japanese are riding the Joba, a $1,400 machine that mimics a bucking bronco; climbing inside the $39,000 Metabology Diet System, a capsule that bathes users in electric currents and steam; and watching military-style boot camp videos.

Mitsuke, a city 160 miles northwest of Tokyo, has even called in superheroes, naming five ``Metabo Rangers'' to crusade for a healthier lifestyle. After completing an education and fitness course, the five tubby, middle-aged men now appear on TV and give newspaper interviews promoting diet and exercise.

``My life used to consist of instant noodles for lunch every day, and I thought a roll with chocolate pudding in the middle was the same as bread,'' says Masanori Murakami, a 43-year-old hotel manager also known as the Red Ranger.

The new exam is part of a government effort to curb spiraling medical costs. Health-care spending rose 23 percent to 33.1 trillion yen ($320 billion) in the decade ended in 2005, according to the Ministry of Health, Labor and Welfare. It's projected to double by 2020 and represent 11.5 percent of gross domestic product.

85 Centimeters

Reduced exercise, the adoption of western foods and an aging population have made Japanese men about 10 percent heavier than they were 30 years ago, ministry statistics show. Women are 6.4 percent fatter.

The ministry estimates that half of men over age 40 and 20 percent of women will be diagnosed with metabolic syndrome. For men, a key yardstick is whether they have a waistline wider than 85 centimeters (33.5 inches). Body mass, cholesterol, blood pressure, blood sugar and smoking will also be taken into account.

Companies will be required to cut the number of overweight workers and dependents by 10 percent as of 2012 and 25 percent by 2015. Failing to do so will result in a surcharge of as much as 10 percent on contributions to a fund for elderly care. Insurance groups paid 6.4 trillion yen into the fund in 2004.

Shunji Hitotsuishi, a branch manager for Shidax Corp., a Tokyo-based caterer, may end up costing his company money in spite of his best efforts. He's dropped 9.1 kilograms (20 pounds) through a company-sponsored program, though his girth remains at 96 centimeters.

Sumo Surgery

``Chronic overeating and a lack of exercise are what got me to where I am,'' says Hitotsuishi, 40. ``These new requirements are a bit strict. It's not an easy task for a guy.''

One sumo wrestler found another way to melt off the pounds. Konishiki, whom fans call ``the Dump Truck'' and who was the all- time heaviest competitor at more than 600 pounds, underwent gastric bypass surgery last month.

Japan's shift toward a preference for slim bodies may not be entirely positive, says Toshio Mochizuki, director of the Medical Urban Clinic in Osaka.

``Currently, society's image of overweight people is not so bad as it conveys the idea of being rich,'' says Mochizuki, author of ``I'm Metabo, So What!'' published in January. ``I'm worried that the overweight will start to be shunned at the workplace and these new rules will make no one want to hire them.''

Fatter Americans

Japanese waistlines are still a long way from those in the U.S., which has the fattest population among developed countries. Two-thirds of Americans over age 20 are overweight, data from National Center for Health Statistics show.

Last month at the Tokyo Health Industry Show, Japan's largest annual expo for health products, vendors on Anti- Metabolic Alley peddled headphones for workouts and pedometers for climbing stairs, as well as slimming drinks and potions.

Ryoichiro Hangui, a Tokyo-based manager at Mizuho Investors Securities Co., a division of Japan's third-largest financial group, has compiled a list of 27 stocks he expects to benefit from increasing fitness awareness.

They include Kao Corp., which markets Healthya brand teas as a diet aid, and Rohto Pharmaceutical Co., producer of a Chinese herbal medicine called Bofutsushosan that promises to whisk fat from the midsection. Rohto has racked up sales of about 20 billion yen since introducing the drug in November 2006, the company said.

``Most people already know if they are overweight, but failing this test is going to make that awareness acute and spur them to take some action,'' Hangui says.

Red Ranger Murakami says he's only dropped about three kilograms in six months and now weighs 80 kilos. While his waist is still larger than 85 centimeters, he's encouraged by an increase in muscle.

``I doubt I'll pass the exam this time around, but I'm not worried,'' he says. ``This is a lifestyle change and an ongoing process.''

To contact the reporter for this story: Patrick Rial in Tokyo at prial@bloomberg.net; Kotaro Tsunetomi in Tokyo at ktsunetomi@bloomberg.net.

Last Updated: March 11, 2008 17:23 EDT