A simple assessment can predict at birth a baby's likelihood of becoming obese during childhood, scientists said on Wednesday.

The formula, available as an online calculator, estimates the child's obesity risk based on its birth weight, the body mass index of the parents, the number of people in the household, the mother's professional status and whether she smoked during pregnancy.

Researchers who published a study of the test in the journal PLOS ONE say they hope it will be used to identify babies at high risk and help families take steps to stop them putting on too much weight before it's too late.

Childhood obesity is a leading cause of early type 2 diabetes, as well as various types of cardiovascular disease, and is becoming increasingly common in developed countries.

According to data from the American Heart Association, almost 18 percent of boys and almost 16 percent of girls aged between two and 19 in the United States are obese. In England, 17 percent of boys and 15 percent of girls aged between two and 15 are obese, according to National Health Service (NHS) data.

"Once a young child becomes obese, it's difficult for them to lose weight - so prevention is the best strategy and it has to begin as early as possible," said Philippe Froguel of Imperial College London, who led the study.

"Unfortunately, public prevention campaigns have been rather ineffective at preventing obesity in school-age children. Teaching parents about the dangers of over-feeding and bad nutritional habits at a young age would be much more effective."

Froguel's team developed the formula using data from a study set up in 1986 following 4,000 children born in Finland.

They were initially investigating whether obesity risk could be assessed using genetic profiles, but the test they developed based on common genetic variations failed to make accurate predictions. Instead, they found that non-genetic information available at the time of birth was enough to predict which children would become obese.

The formula proved accurate not just in the Finnish children they studied, but also in further tests using data from studies in Italy and the United States.

"This test takes very little time, it doesn't require any lab tests and it doesn't cost anything," Froguel said. The calculator is available here.

Although the team's work using common genetic variants did not prove to be helpful for predicting childhood obesity, they said about one in 10 cases of obesity are caused by rare mutations that seriously affect appetite regulation.

The researchers said tests for these types of mutations could become available to doctors in the next few years as the cost of DNA sequencing technology falls.

Image Source / Getty Images file

In the 13 heaviest states, 60 percent of residents will be obese in less than two decades if current trends continue, finds a new report.

Think Americans are fat now? After all, a third of us are overweight and another 35 percent are obese. But a report out Tuesday projects 44 percent of Americans will be obese by 2030.

In the 13 worst states, 60 percent of the residents will be obese in less than two decades if current trends continue, the report from the Trust for America’s Health projects. That’s not chubby or a little plump – that’s clinically obese, bringing a higher risk of heart attacks, strokes, diabetes, several forms of cancer and arthritis.

“The initial reaction is to say, ‘Oh it couldn’t be that bad’,” says Jeff Levi, executive director of the Trust for America’s Health. “But we have maps from 1991 and you see almost all the states below 10 percent.” By 2011 every single state was above 20 percent obesity, as measured by body mass index (BMI), the accepted medical way to calculate obesity. Those with a BMI or 30 or above are considered obese.

In August, the Centers for Disease Control and Prevention reported that 12 states have an adult obesity rate over 30 percent. Mississippi had the highest rate of obesity at 34.9 percent. On the low end, 20.7 percent of Colorado residents are obese. CDC projections for obesity resemble those in Tuesday's report - it projects 42 percent of adults will be obese by 2030.

The problem isn’t just cosmetic. “The number of new cases of type 2 diabetes, coronary heart disease and stroke, hypertension and arthritis could increase 10 times between 2010 and 2020 — and then double again by 2030,” the report projects.  “Obesity-related health care costs could increase by more than 10 percent in 43 states and by more than 20 percent in nine states.”

That’s bad news when states are already strapped to pay for public health programs such as Medicaid and the federal government is struggling to fund Medicare.

Over the next 20 years, more than 6 million patients will be able to blame obesity for their diabetes, 5 million will be diagnosed with heart disease and 400,000 will get cancer caused by obesity.

And some of them are frighteningly young.

"Now I am seeing 25-year-olds weighing 350 pounds who present with chest pain or shortness of breath," says Dr. Sheldon Litwin, a cardiologist at Georgia Health Sciences University. “Everything from the heart disease process to its diagnosis and treatment are affected by obesity. We see it every day. This really is the number-one issue facing us," added Litwin, who worked on one of a series of obesity studies published in this week’s issue of the Journal of the American Medical Association.

The trend is not inevitable, according to the report, entitled “F as in Fat.” Some programs are beginning to make a dent in the rising rates.  “We certainly see, in some communities, the beginning of some changes,” says Levi. “We know what some of the answers are.”

Convicted killer: I'm too obese to be executed

For instance, making it easier for people to exercise day in and day out, and making it easier to get healthy food. “A large-scale study of New York City adults found that increasing the density of healthy food outlets, such as supermarkets, fruit and vegetable markets, and natural food stores is associated with lower BMIs and lower prevalence of obesity," the report reads.

What about initiatives like New York’s controversial ban on the largest sodas? “Every community is going to experiment with different approaches. It is going to be very interesting to see what happens in New York and whether this makes a difference,” Levi said.

New York’s health commissioner, Dr. Thomas Farley, defends the move in the medical journal’s obesity issue. "How should government address the health problems caused by this successful marketing of food? To do nothing is to invite even higher rates of obesity, diabetes, and related mortality,” he wrote.

Trust for America's Health

Many studies have also shown that people who live in big, walkable cities such as New York and Washington D.C. are thinner than their rural and suburban counterparts, and it’s almost certainly because they walk more and use public transportation instead of sitting in cars.

If everyone lost just a little weight, the savings would be enormous, the study predicts.

“If we could lower obesity trends by reducing body mass indices (BMIs) by only 5 percent in each state, we could spare millions of Americans from serious health problems and save billions of dollars in health spending —between 6.5 percent and 7.8 percent in costs in almost every state,” the report says.

Education can’t hurt, either. The more educated people are, the less likely they are to be obese. Higher-earners are also thinner. “More than 33 percent of adults who earn less than $15,000 per year were obese, compared with 24.6 percent of those who earned at least $50,000 per year,” the report notes. And several studies have shown that people who eat more fruits and vegetables are thinner, as well as healthier. “Seven of the 10 states with the highest rates of obesity were also in the bottom 10 for fruit and vegetable consumption,” the report says.

Levi believes it’s worthwhile targeting kids the hardest. New nutritional guidelines for schools will help, he said, as will initiatives to restore recess and physical education classes. Beverage makers have agreed to replace sugary sodas in vending machines with water and other low-calorie drinks. “It is as simple as an hour a day less of screen time and one less sugar beverage,” Levi says.  “Just 120 calories can make a big difference as to whether a kid crosses over from being normal weight into overweight and obesity.”

Another study in the Journal of the American Medical Association showed that kids who exercised 20 minutes a day lowered an important measure of diabetes risk by 18 percent. Exercising 40 minutes a day cut the risk by 22 percent. The researchers also noted it’s important to make exercise fun for kids

"Regulation sports tend to have kids standing around a lot waiting for the ball. We had enough balls so everyone was moving all the time," said Dr. Catherine Davis of Georgia Health Sciences University. "It had to be fun or they would not keep coming.”

For some people, drastic measures remain an option. One study in the Journal shows that gastric bypass surgery is a viable option. And two doctors present opposing views over whether the Food and Drug Administration holds obesity drugs to an unreasonably high standard. On Tuesday, one of the newest obesity drugs hits the market - Qsymia, made by Vivus.

Are you obese? The National Institutes of Health has a BMI calculator here. http://www.nhlbisupport.com/bmi/

If you’re 5 feet 6 inches tall, you become overweight at 160 pounds (a BMI of 25.1) and obese at 192 pounds, when your BMI grows to 30.1.

Trust for America's Health

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By Joyce Ho and Dr. Nancy Snyderman
NBC News

The nation’s ever-growing obesity epidemic may be far worse than originally thought. New research demonstrates that even people with a healthy Body Mass Index, a commonly used scale to measure body fat, could actually be obese and at risk for a host of complications.

A study published Monday in the journal PloS One found that using BMI as an indicator of obesity actually misclassifies 39 percent of Americans as “overweight” rather than “obese.” And because BMI doesn’t distinguish between fat and muscle, some people with normal BMIs may have dangerously high amounts of fat in their bodies.

Without an accurate measurement of body fat, the researchers say, millions of people don’t know they are at high risk for a number of obesity-related diseases.

“The fat is what causes heart disease, cancer, menstrual problems, depression, anxiety, and a host of medical problems,” said Dr. Eric Braverman, a professor at Weill Cornell Medical School and co-author of the study. “So if you want to save society from a lot of illnesses …  you have to identify how much fat they have.”

More than one in three adults in the U.S. are obese, as defined by a BMI of 30 or higher, according to the Centers for Disease Control. Obesity measurement, however, has been a controversial topic for years, and the widely-used BMI calculation has been called outdated by experts.

BMI is calculated through a simple formula: weight divided by height squared. The ease of calculation made this formula popular, even though it’s nearly 200 years old. In Braverman’s study, researchers compared the BMI with a different measurement, the Dual Energy X-ray Absorptiometry (DXA) scan. DXA scans, commonly done in women to check for osteoporosis, measure percentage of body fat, muscle mass, and bone density.

Of the 1,393 people studied, 26 percent were classified as obese when body fat was measured with BMI, whereas 64 percent of them were considered obese when measured with DXA. The misclassification was observed more often in women and increased with advancing age: 48 percent more women between the ages of 50 to 59 were classified as obese when measured with DXA instead of BMI, and among women ages 70 and above, 59 percent more were considered obese after getting a DXA scan. 

According to the authors, BMI is an inaccurate measure for obesity – but especially in this demographic, because as women age they lose more muscle to fat than men. BMI, which does not distinguish between muscle or fat, does not reflect this bodily change. 

“BMI doesn't tell you how much fat … you have,” said Braverman. “So without knowing how much fat you have, you can't really save people from illness. It is the number one predictor of who's going to live or die.”

Researchers also tracked blood levels of leptin, a hormone produced by fat cells that regulates hunger and energy expenditure. Increased blood leptin levels correlated well with DXA scan results, highlighting the potential for a simple leptin blood test to be a measurement for obesity.

Based on these findings, Braverman and his co-author Dr. Nirav Shah, the current New York state health commissioner, suggest lowering the BMI definition of obesity from 30 to 24 in women and down to 28 in males. Under these suggested guidelines, a woman who is 5’ 6” and 150 pounds would be considered obese. Under the current BMI standards, the same woman would be considered healthy.

“Fat is costing the country a fortune, by not measuring it,” said Braverman. “A dollar blood test and doing our bone density scans with body fat scans at the same time is going to save us an enormous medical cost in the end.”

NBC’s Stacey Naggiar, Chiara Sottile and Joo Lee contributed to this report.

Read more from msnbc.com:

• America’s fattest cities
• Size matters for obese cancer patients’ drug dose
• U.S. advisers back obesity pill