Diet and nutrition are key to maintain human health. Westlake N-of-1 Trials for Macronutrient Intake (WE-MACNUTR) trial investigates individualized postprandial glycemic responses to different proportions of dietary fat and carbohydrates intake using an n-of-1 experimental study design. The experimental diets are isocaloric high fat, low carbohydrate (HF-LC) or low fat, high carbohydrate (LF-HC). With standardized intervention and strictly controlled eating behaviors, the WE-MACNUTR study identifies specific HC-responders and HF-responders in terms of postprandial glucose response.

This is a follow-up study offered to participants who have completed the WE-MACNUTR study in 2019. Volunteers will be asked to participate in four 5-d periods while wearing glucose monitors (Abbott Freestyle Libre) with the following experimental sequence: 1) a washout diet, 2) HF-LC or LC-HF diet, 3) a washout diet, 4) HF-LC or LC-HF diet. The experimental diet will be randomly assigned. Participants will be asked to provide a fasted blood sample and to collect fecal, urine and saliva samples at each visits.

This study is a two arm dietary intervention study. Participants will be recruited from the WE-MACNUTR study based on the defined inclusion and exclusion criteria. The study duration will last up to 21 days.

Volunteers will be asked to participate in four 5-day periods while wearing glucose monitors (Abbott Freestyle Libre) with the following experimental sequence: 1) a washout diet, 2) HF-LC or LC-HF diet, 3) a washout diet, 4) HF-LC or LC-HF diet. The experimental diet will be randomly assigned.

Participants will enter the study on a usual (washout) diet and will have a 5-day run in period for baseline data collection. Participants will be asked to follow dietary guidance and consumed a healthy and balanced diet during this period.

Inclusion Criteria:

• Participants have completed WE-MACNUTR trial in 2019
• Participants have no traveling plans within 1 months
• Participants are able and willing to comply with the study protocol and provide informed consent

Exclusion Criteria:

• Refuse or are unable to provide informed consent to participate in the study
• Have long-term gastrointestinal diseases and take daily relevant medications
• Have taken antibiotics in the last 2 weeks
• Have type 2 diabetes and are taking medications or other treatments
• Have chronic or acute liver disease and are taking medications or other treatments
• Have cardiovascular diseases and are taking medications or other treatments
• Have kidney disease and are taking medications
• Suffer from chronic anxiety or depression, or other critical neuronal disorder and/or history of relevant medication
• Are pregnant or lactating, or are planning to be pregnant in the next 3 months
• Diagnosed with an eating disorder (e.g. anorexia nervosa or bulimia nervosa)
• Are vegan, or unwilling to consume foods provided in the study
• Have history of alcohol or drug addiction, or smoke above 15 cigarettes per day