Is a greater body mass index (BMI) related to insensitivity to internal signals? Background: There is circumstantial evidence that obese individuals may be less sensitive to internal signals of hunger and satiety than non-obese individuals. Delado-Aros et al., (2004) found a significant relationship between BMI and feelings of fullness after a meal – that is the larger the person (i.e. higher BMI) the less likely they were to report feeling full. Many influential researchers (e.g. Stunkard) have argued that individuals who are obese may experience constant hunger, although there is little hard data to actually back this assertion. However, we do know that obese individuals must consume more food – so it is reasonable to assume that they (a) may feel more hungry and (b) may be less sensitive to feelings of fullness – and so feel hungry again more quickly. Here, we will look to see if ratings of hunger and fullness (satiety) are related to BMI – that is do people with a higher BMI report feeling hungrier before a meal and less full after a meal, than people with a lower BMI? Method: You will need to find two people who are as similar as reasonably possible and who are not dieting, but who differ in BMI. You will then need to calculate each persons BMI (body mass in Kg divided by their height in M squared). Next, get them to rate how hungry they are just before they have their main meal of the day (10cm scale from Not hungry at all to Extremely hungry) and then again just after they have completed their main meal (see attached scale). You will also need to estimate the Kcals consumed in their meal (see https://www.calorieking.com which has a pretty good info on the caloric value of foods). Issues to consider: You will need to think what criteria to base similarity upon – age, gender etc. Also, you need to be convinced that this will be their main meal of the day. How will you estimate the number of Kcal consumed in the meal? On a different tack – will people accurately report their height and weight – and could they be upset by a request for this information? If so how would you deal with this? Analysis: One obvious problem is that people normally eat different quantities of food at their main meal – and this will then influence any change in hunger/satiety. That is if a person happened to eat a big meal they would obviously feel fuller after the meal and relatedly, they may have felt hungrier before it. To get around this we will use a satiety quotient. To calculate your satiety quotient, subtract the hunger rating obtained before the meal with the rating obtained after the meal. Then divide this value by the number of Kcals that you estimate they consumed in that meal. An example: if we have a 70 kilo person who is 1.7 M tall, they have a BMI of 70/(1.7 x 1.7) = 24.2. For dinner they had fried battered fish (75g; 194Kcal) and chips (150g; 570Kcal), followed by ice cream (70g; 201Kcal) – total is 965Kcal. Their hunger rating was 90 (measured in mm before the meal) and 40 afterwards. Their satiety quotient is then 90 minus 40 divided by 965 = 0.052. In class you will then (using all the data) need to calculate the correlation between BMI and the satiety quotient. Here an example of how to do it: (look at the bottom page of the file attached “tutorial 7 and 8 – internal signals – hunger and satiety ” The photos attached are from tutorials and are both information about what we did, how we did it and results from it. Please analyse carefully, do NOT copy every word, but rather understand the stats/numbers and write in own word what these means. only Reading and ONLY reference: Delgado-Aros, S. et al., (2004). Independent influences of body mass and gastric volumes on satiation in humans. Gastroenterology, 126, 432-440.
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