Asthma has skyrocketed in the U.S. – the prevalence of asthma doubled between 1986 and 2005. Obesity is known to mechanically compromise proper function of the lungs and airways and is associated with asthma-related inflammation. Increased prevalence of asthma in obese individuals has been demonstrated in several studies, and there exists a dose-response relationship such that as BMI increases, asthma risk increases. Obesity is thus an independent risk factor for asthma. It is now widely believed that the rise in childhood obesity is a causative factor for the recent rise in asthma. [1, 2]
In addition to obesity, metabolic abnormalities in children and teens, such as high cholesterol, high triglycerides, and hyperinsulinemia, regardless of body weight have now been associated with asthma. This means that even if a child is of normal BMI, the standard American diet is likely taking its toll on lung function, producing early metabolic abnormalities that may set the stage for asthma, obesity, diabetes, and other chronic disease. 
In adults who already have asthma, previous data has been inconclusive when trying to determine whether obesity affects asthma severity. However, there is a strong connection between poor nutrition and asthma, including evidence that a single high-calorie, low-nutrient meal can spark airway inflammation, which can exacerbate asthma symptoms. Asthmatic adults consuming a single high-calorie, low nutrient meal, high in animal protein and added fat (1,000 calories worth of fast food hamburgers and hash browns) showed increased airway inflammation four hours later. Researchers compared this to a 200 calorie meal, which did not increase inflammation. 
Obesity, resulting from the cumulative effects of years of overeating low-nutrient, high-calorie food is a risk factor for asthma. However, deleterious effects of a low-nutrient diet on lung function occur even in the short term, and can begin early in life. Collectively, these studies tell us that asthma is another disease whose major causes include poor nutrition and a sedentary lifestyle.
Since asthma is both a lifestyle- and inflammation-related disease, dietary changes and weight loss are effective at improving asthma symptoms. A high-nutrient diet floods the body with protective micronutrients, reduces inflammation, and promotes weight loss – allowing the body to resolve the risk factors for asthma mentioned above (obesity, high cholesterol, etc.). Dr. Fuhrman has had much success using a high-nutrient diet to treat patients with asthma – many recover completely and no longer need asthma medication. He recently conducted a survey of hundreds of nutritarians, in which 82% of respondents with asthma reported a significant improvement in their symptoms after switching to a high-nutrient diet. Here is just one example:
“Dr. Fuhrman has truly been a blessing to me and my family. My husband has lost weight as so has my 11-year-old son. My son had put on a lot of weight and has asthma, making it almost impossible to complete the running portion of a physical challenge in gym class. But a couple of weeks ago, I had tears in my eyes as he crossed the finish line without wheezing!
I have more energy and have never felt this good. I tell everyone I know about Eat To Live and Eat For Health and will continue to sing Dr. Fuhrman’s praises.
1. Sutherland, E.R., Obesity and asthma. Immunol Allergy Clin North Am, 2008. 28(3): p. 589-602, ix.
2. Canoz, M., et al., The relationship of inflammatory cytokines with asthma and obesity. Clin Invest Med, 2008. 31(6): p. E373-9.
3. Cottrell, L., et al., Metabolic Abnormalities in Children with Asthma. Am J Respir Crit Care Med, 2010.
4. High-fat meals a no-no for asthma patients, researchers find. ScienceDaily. , in American Thoracic Society 2010 International Conference. 2010: New Orleans, LA.