This study will test the effect of diet on asthma in individuals with obesity.

This is a crossover design pilot trial that will recruit 12 adults with obesity and asthma. Participants will undergo screening and a lead-in period before being randomized to a series of three, 7-day diets with a 7+ day washout period between each diet. Asthma control and lung function will be assessed at the completion of each diet.

The goal of this pilot trial is to understand the effect of diet on asthma and conduct an exploratory analysis on factors that may predict the response to diet.

Inclusion Criteria:

• Age: 18-65 years
• BMI: 30-45 kg/m2
• asthma diagnosed by medical specialist (confirmed in medical history)
• partly controlled or uncontrolled asthma by Asthma Control Test score ≤22
• owns a device compatible with ZEPHYRx platform
• stable asthma medication use (no change in the past 2 months).

Exclusion Criteria:

• Diabetes or using diabetes medications that may lower blood glucose levels
• point of care fasting blood glucose ≥126 mg/dl or triglycerides ≥400 mg/dl
• current smoking or smoking history of greater than 10 pack-years
• other significant respiratory or cardiac disease or the presence of clinically important comorbidities, e.g., COPD, renal failure, liver disease; uncontrolled hypertension defined as systolic blood pressure ≥160 mm/Hg, or diastolic blood pressure ≥100 mm/Hg
• pregnant or nursing women
• food preferences or allergies inconsistent with study diet capabilities
• noncompliance with lead-in period requirements.

Study data will be provided upon request and approval by study PI.

Participants will not be made aware of the diet allocation. However, due inherent differences in macronutrient content of the diets, participants may perceive differences in the quantity of various food groups or in the taste, texture or smell of foods present in the diet. To address this, diets will be designed to minimize noticeable differences for the participant. The investigator and outcomes assessor will remain fully masked to diet provision.