By 2010 that number has risen to 33.8% of adult Americans. You can see a slideshow map of the USA at http://www.cdc.gov/obesity/data/trends.html which will show you how obesity in the USA has gone from 1 in 11 adults in to 1 in 3.
Factor V Leiden usually effects Caucasians under the age of 45. It only effects people whose parents both had the gene, and even then only effects 1 out or 12 people who inherit the "double gene". Only 1% of the Caucasian population in the USA has the "double gene" and only 0.083% of the population is effected by it. Only 1 in 1200 people.
The end result is only approximately 167,000 people who are effected by "double gene" for Factor V Leiden.
Note: Since it is genetic there is no "cure", but there is treatment for Factor V Leiden:
Treatment of a patient with Factor V Leiden requires anticoagulation and cardiovascular exercise. This is accomplished by several different medications: 1) heparin, 2) warfarin and 3) low-molecular-weight heparins. These medications are generally used for 3-6 months. Patients under treatment should do cardiovascular exercise twice per day for approx. 30 minutes each time.
The use of long-term (over the limit of 6 months) anticoagulation has an approximately 3% risk per year of having a hemorrhage and thus patients should routinely go off the medication for 2 months at a time, but continue cardiovascular exercise treatment during that time period. The accepted method of treatment is 4 months on anticoagulation medication and 2 months on a non-sugar based placebo, repeated continuously in combination with daily cardiovascular exercise.
So Factor V Leiden does not explain America's obesity problem because its #1. extremely rare and #2. treatable using medication and exercise. That and other illnesses does not explain the almost 100 million Americans (children and adults) who are obese.
Diabetes is another scapegoat, but the problem is that it is "Type 2 Diabetes" that most obese people have. Type 2 Diabetes is caused by being overweight, not the other way around.
So what about the rest of the world that isn't suffering from such shockingly high rates? What are they doing so differently?
#1. The rest of the world gets more exercise. The average American exercises less than 19 minutes per day. That is the AVERAGE. Which means healthy Americans are exercising an hour or more per day.
#2. The rest of the world eats less sugar, carbohydrates and fat in their food. The average American consumes 3,790 calories per day (2002 statistic). The healthy level is 1800 to 2000 calories per day. Remember that 3,790 is the average. This means some Americans are consuming a lot more than 4,000 calories.
So America's obesity is really an issue of LIFESTYLE. They are overeating and barely exercising.
Compare this to 150 years ago when most Americans were farmers, worked outside most of the day, got lots of exercise, ate a decent meal and didn't pig out.
Today the average American spends 8.5 hours per day in front of either a computer screen or a TV screen. Assuming they spend another 8 hours sleeping, another 4 hours eating, bathing and doing household chores, 1 hour in traffic going to and from work or school, what are they doing for the other 2.5 hours?
Well since Americans only spend 19 minutes exercising I guess whatever they are doing must be more important than their health.