A randomized cross-over design aims to investigate chewing activities between healthy vs. overweight and determine effects chewing times on energy intake and postprandial plasma glucose and insulin. Forty-one participants were allocated into lean and overweight groups according to BMI. Phase I, Bite size (g/bite), bite rate (bites/min), chewing frequency (chews/min), and chews (chews/g food) were recorded after a sandwich breakfast. Phase II, gram of sandwich eaten ad libitum after 15 and 50 chew per bite (number from phase I) were recorded. Postprandial plasma glucose and insulin were examined at 0 (baseline), 30, 60, 90, 120 and 180 min.

Forty-one eligible participants were divided into 2 groups; lean and overweight according to their BMI [lean BMI (kg/m2) ≥ 18.5 and < 23, overweight BMI ≥23]

Phase I: investigate the differences of chewing activities between healthy weight and overweight participants.

The day before the clinic visit, participants were requested to consume only portion control of fried rice with egg for their dinner at 6 -7 pm. No other foods or drinks were allowed after provided dinner. The next morning, participants arrived at the clinic between 7-8 am after a 12 hours overnight fast and a 24 hours period without exercise. Sandwich was served with 300 ml. of water for breakfast ad libitum. Foods consumed were recorded. A digital camera recorded each participants chewing activities including bite size (g/bite); the ratio of food weight to bite number, bite rate (bites/min); the ratio of bite number to meal time, chewing frequency (chews/min); the ratio of chews to meal time, chews (chews/g food); the ratio of chews to meal weight.

Phase II: investigate the effects 15 chews and 50 chews on energy intake, hunger, satiety, appetite, postprandial plasma glucose and insulin in both healthy weight and overweight participants Participants were allocated into 2 groups of a 15 chews and 50 chews per bites with 2 weeks of wash-out period. The day before the clinic visit, participants were requested to consume only portion control of fried rice with egg for their dinner at 6 -7 pm. No other foods or drinks were allowed after provided dinner in order to prevent confounding factors of previous food consumption. On the next day, participants arrived at the clinic between 7-8 am after a 12 hours overnight fast and a 24 hours period without exercise. At clinic visit, baseline characteristics including anthropometry, hunger, satiety, appetite, and plasma glucose and insulin concentrations were collected before breakfast was served. Participant was requested to rate their hunger, satiety and appetite using a visual analogue scale (VAS) questionnaire.

After collecting baseline indicators, participants were served an ad libitum sandwich and 300 ml water for breakfast. Participants had to finish their breakfast within 20 min after first bite. VAS questionnaire and blood samples of postprandial glucose and insulin were examined at 0 (baseline) 30, 60, 90, 120 and 180 min after test meal. Blood samples was collected from indwelling catheters at mentioned time points.

Inclusion Criteria:

• non-smoking
• eating breakfast regularly
• not allergic to any food
• no eating disorders
• weight stable over the past 3 months

Exclusion Criteria:

• have dental problem
• taking any medications or dietary supplements that may confound any study indicators