The purpose of this research is to determine whether extra betaine and choline influence metabolic health in adults with overweight and obesity.

Betaine (N,N,N-trimethylglycine or also glycine betaine) is a derivative of choline that functions as an organic osmolyte and participates in one-carbon metabolism as a methyl donor. Betaine is naturally found in beets, wheat and spinach and sold as a food supplement without prescription. Choline is recognized as an essential nutrient that is found in various foods including eggs, nuts and beef, with the major form of choline in food found as phosphatidylcholine. In addition to being oxidized to the methyl donor betaine, choline is a precursor of several compounds involved in neurotransmitter synthesis, lipid metabolism and transport as well as the structural integrity and signaling of cell membranes. Previous studies have reported alterations in one-carbon metabolites in response to a single meal containing different forms of choline, with interindividual variability dependent on genetics and gut microbiota composition. This study will extend to longer-term impact of different forms of choline (betaine as oxidized choline and choline provided from food) with a focus on overweight and obesity, which comprise a predominant portion of the population in North America. The objective of this study is to determine the effect of betaine supplementation with or without food-form choline (eggs) on metabolic health in adults with overweight and obesity. A randomized crossover study design will be employed, which men and women of age 18-70 years with BMI 25-35 kg/m2 will participate in a 14-week study consisting of three 4-week dietary periods: 1) daily consumption of 3 grams of betaine supplement with no eggs; 2) daily consumption of 3 grams of betaine supplement with 3 whole eggs; and 3) daily consumption of 3 grams of cellulose supplement with no eggs, in a random order, each dietary period separated by a 1-week washout break. Blood, urine and fecal samples as well as anthropometric measurements will be collected at baseline, then at weeks 4, 9 and 14. The collected biological samples will be used to measure glucose and lipid markers, one-carbon metabolites and profiling of gut microbiota and genotype to determine interindividual differences in metabolism.

Inclusion Criteria:

• Male or female participant of any race or ethnicity between 18-70 years of age (inclusive) at the time of informed consent
• BMI between 25-35 kg/m2
• Non-smoker
• Willing to consume 3 eggs per day for one dietary period of 4 weeks
• Willing to avoid eggs during the rest of the study including washout period breaks except for eggs that are provided
• Willing to fast before the baseline and dietary period lab visits
• Willing to provide a 24-hr prior day food record at the dietary period lab visits
• Willing to provide or collect biological specimen samples at the baseline and dietary period lab visits
• Willing to follow the study protocol including maintaining usual lifestyle during the entire study

Exclusion Criteria:

• Male or female < 18 years or > 70 years of age at the time of consent
• BMI < 25 kg/m2; or BMI > 35 kg/m2
• Pregnant or planning to become pregnant during the course of the study; currently breastfeeding or postpartum < 6 months
• Use of hormone therapy including birth control pills
• Follows a vegan diet
• Current smoker (any form of nicotine, e-cigarettes, etc)
• Use of recreational drugs (may affect metabolic pathway for choline)
• Presence of chronic illnesses, e.g., heart disease, diabetes, cancer, celiac disease, inflammatory bowel disease (Crohn's disease and ulcerative colitis), gastrointestinal liver or kidney diseases or alcoholism
• Diagnosis of trimethylaminuria (genetic disorder affecting choline use in body)
• Use of antibiotics in the last 2 months
• Use of prebiotics, probiotics or dietary fiber (i.e., Metamucil) supplements in the last 2 months
• Have allergies to eggs or any anaphylactic food allergies
• Have a schedule or lifestyle patterns incompatible with the study protocol

Supplements will be double-blinded, which the order of dietary periods will not be revealed to participants until after the study is completed. Care provider, investigator and outcomes assessor who will be involved in collecting study data will not know the supplement assignment.