Influence of the Constancy of Daily Meal Pattern on Energy Balance, Glucose Profiles an Appetite in Healthy Women

Background:

Previous work in our laboratory has shown that there are potentially important negative health consequences associated with irregular eating. Greater fasting levels of total-cholesterol and LDL-cholesterol, a decrease in meal induced thermogenesis, and as a greater insulin response to a test drink, were observed in healthy women following a two-week period of irregular meal pattern (variable number of daily meals; from 3 to 9); this was in contrast to a regular pattern of six daily meals. In addition a greater energy intake was self-reported during irregular compared with the regular meal pattern. Subsequent studies have confirmed such an effect in overweight subjects and also provided evidence of alterations in subjective appetite which may influence ad-libitum food intake. The present project will study normal weight subjects, and incorporate energy expenditure measurement under free living conditions using a novel technique (SenseWear armband, SWA), continuous glucose monitor, and obtain more detailed information about appetite and food intake.

Aims:

To investigate the effects of regular and irregular meal pattern on energy expenditure, energy intake, , Glucose profiles and subjective appetite in healthy normal weight women.

Experimental protocol and methods:

Normal weight women (BMI 18.5-25) who are otherwise healthy will be studied during the early phase of their menstrual cycle (first week).

Subjects will be initially screened and then complete a 7 days food diary before participating in the study which will last for a total of 6 weeks. During the first 2 weeks participants will adopt one of two meal patterns, followed by a two-week washout period on habitual diet and meal pattern, before undertaking a second 2-week intervention following the second meal pattern. The meal patterns will be 1) regular - 6 daily meals or snacks for 2 weeks, or 2) irregular - a different number (between 3 and 9) of meals/snacks every day. All foods to be consumed during weeks1, 2, 5 and 6 will be provided free of charge, and will comprise foods commonly consumed in the British diet in amounts designed to keep body weight constant during the study. Participants will complete food diaries over the study period. Subjects will wear a SenseWare device (attached to an upper arm) to allow physical activity and energy expenditure to be estimated in weeks1, 2, 5 and 6. Subjects will attend the lab on the 6th day of each intervention phase to have a continuous glucose monitoring probe inserted in their subcutaneous tissue over the abdomen and attached to a small monitor. Subjects will also need to measure their blood glucose four times a day using a fingerprick to obtain a droplet of blood and analysing it with a pocket glucose analyser. After three seven subjects will be asked to come back to have the device removed.

Subjective appetite (hunger, fullness, etc.) will be assessed using visual analogue scales (VAS) during the intervention (at the end of the first and second week) Before and after each intervention period, participants will visit the laboratory after fasting overnight. At 8:30 am a cannula will be inserted into a hand vein, with the hand placed in a heating box, for subsequent blood sampling. Indirect calorimetry will be performed to determine energy and changes in the thermic response to a milkshake test drink providing 10 kcals/kg body weight, and comprising 35% of energy as fat, 15% as protein, and 50% as carbohydrate. The SWA will be placed on the upper left arm to estimate energy expenditure. Subsequent blood samples will be obtained every 15 minutes during the next 3 hours in which indirect calorimetry and SWA will be measured concurrently. Fasting blood samples will be used to measure total-, high density lipoprotein (HDL)-, and low density lipoprotein (LDL)-cholesterol, triglycerides, glucose and insulin. Blood samples obtained after the test drink will used to measure glucose, insulin and hormones related to appetite. After that, a test meal (pasta) will be provided as ad-libitum meal and subject will be asked to fill VAS to assess subjective appetite sensations.