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Thinner is better to curb global warming, study says

Story Highlights

* Transporting heavier people requires more fuel, generating more
greenhouse gas
* Study compared BMI distribution in UK in 1970s with predictions for 2010
* Governments should encourage active transportation, study author says

By Elizabeth Landau
CNN
(CNN) -- Here's yet another reason to stay in shape: Thinner people
contribute less to global warming, according to a new study.

Researchers at the London School of Hygiene and Tropical Medicine published
a study showing that, because of food production and transportation
factors, a population of heavier people contributes more harmful gases to
the planet than a population of thin people.

Given that it takes more energy to move heavier people, transportation of
heavier people requires more fuel, which creates more greenhouse gas
emissions, the authors write.

"The main message is staying thin. It's good for you, and it's good for the
planet," said Phil Edwards, senior lecturer at the London School of Hygiene
and Tropical Medicine.

The study offers this novel approach to the global warming problem as U.S.
lawmakers discuss the future of climate change legislation. This week, the
the House Energy and Commerce Committee is scheduled to begin on a
comprehensive energy and climate bill. On Friday, the Environmental
Protection Agency announced that six greenhouse gases pose potential health
hazards, an announcement that could prompt the regulation of the gases.

More than 1 billion adults worldwide are overweight, and about 300 million
are obese, the study said. Generally, the body mass index, a measure of
obesity, is increasing in most countries worldwide, from China to European
countries to the United States.

BMI is going up because of the availability of food and motorized
transportation, Edwards said. People are less active now than they were 30
years ago, and the prevalence of fast food has given people less healthy,
more energy-dense options.

Using statistical models, the authors compared the distribution of BMI in
the United Kingdom in the 1970s -- when 3.5 percent of the population was
obese -- with a prediction for the country's BMI distribution in 2010,
reflecting 40 percent obesity.

"In terms of environmental impact, the lean population has a much smaller
carbon footprint," Edwards said.

The population with 40 percent obese people requires 19 percent more food
energy for its total energy expenditure than the population with 3.5
percent obese people, the study showed.

This 19 percent increase in food consumption translates into an increase of
270 million metric tons of greenhouse gas emissions, the study said.

"The findings make sense and highlight an important global co-benefit of
losing weight, along with the significant personal health benefits," said
Patrick Kinney, associate professor at Columbia University's Mailman School
of Public Health, who was not involved in the study.

In terms of obesity rate, the U.S. population is not far off from the
overweight population model in this study. The country has 33.3 percent
obese people, according to the Mayo Clinic.

The study suggests that governments have a responsibility to encourage
people to be more physically active, Edwards said. Active transportation,
such as cycling and walking, helps maintain a healthy weight but requires
safe streets, he said.

"If the government wants to promote active transport, which would be good
for the environment and for individual health, it needs to make the
environment safe to do that," he said.

Although climate change has come into the forefront as a major world
problem recently, this is not the first time scholars have thought about
the connection between fossil fuel and body fat.

In 1978, a year the United States experienced an oil shock, a study in the
American Journal of Public Health showed that if all overweight people in
the country aged 18 to 79 reached their optimal weight, the resulting
energy savings would equal 1.3 billion gallons of gasoline.

After the dieting period, about 750 million gallons of gasoline would be
saved every year, said the authors, Bruce Hannon, professor at the
University of Illinois, Urbana-Champaign, and Timothy Lohman, now professor
emeritus at the University of Arizona.

Today, research has shown that the obesity epidemic costs the United States
about $100 billion a year, said Dr. Martin Donohoe of Portland State
University, who runs the Web site Public Health and Social Justice. In
terms of energy expenditure, the average food product travels 1,500 miles
to get to your table, he said.

Some measures to curb obesity include making healthier meals available in
schools, putting nutritional information on food packages and menus, and
banning trans fats, he said.