Lecture notes
Nutrition and Behaviour Psychology - Part 8 Lecture Notes
- Module
- Nutrition And Behaviour
- Institution
- Swansea University (SWAN)
Nutrition and Behaviour Psychology - Part 8 Lecture Notes
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Nutrition and BehaviourMarch 2017
Lecture 8: Food intake and Obesity
Introduction:
Hunger – one of the body’s strongest and most beneficial stimuli – helps insure that you consume enough calories
for the needs. However, it also works against you when you're trying to lose weight. You could easily lose weight just
by eating less, but the less that you eat or the longer you postpone eating, the hungrier you become, and the longer
it takes your hunger to subside once you do begin to eat. So the hungrier you are, the more likely it is that you'll
overeat, consuming extra Calories that can quickly slow or reverse your weight loss.
As you know, the only way to end hunger is to eat. Eating provides satiety - a pleasant feeling of fullness and the
corresponding reduction of hunger. But did you also know that some foods are better than others for satisfying your
hunger? A baked potato, for example, will probably "fill you up" much better than a serving of candy that has the
same number of Calories.
Impact of Nutrients on Food Intake
Items/Questions for consideration and discussion:
What influence have macronutrients and/or micronutrients been shown to have on food intake?
What indications is there that sugar and/or fat influence food intake?
How could (mechanistrically) fat and/or sugar influence food intake?
,Satiety → Experience after a meal – how long before you feel hungry again.
Satiation → Occurs during a meal – the point at which you have had enough to eat.
Can satiety be predicted?
If there was a way of predicting satiety, we'd be able to select foods that satisfied our hunger, but contained fewer
Calories. These foods would greatly improve our ability to create meals that were effective for weight loss.
Because of the strong relation between satiety and a food's weight, some researchers have recommended the
consumption of foods with low Caloric densities - i.e. foods that have the fewest total Calories per gram. One of the
most notable of these researchers is nutritionist Barbara Rolls, Ph.D., whose prior best-selling diet book, Volumetrics,
explained her use of low Caloric density foods for weight loss. A more recent diet that makes use of low Caloric
density foods is the Negative Calorie Diet. There are also many specialty diets that use a low Caloric density
approach. Included among these are the cabbage soup diet and the grapefruit diet.
Unfortunately, Caloric density alone is not a reliable predictor of satiety, and it overlooks many enjoyable foods that
would make wonderful additions to your diet. What you need is a better way to predict satiety.
Holt et al. (1995):
Satiety index reflects the fullness produced by a set portion of foods over two hours, i.e. short term satiety.
Consumed 1000kj (240 calorie) portions of 38 different foods.
Satiety ratings were obtained every 15 minutes over 120 minutes.
Then ate ad libitum (at one’s pleasure, their choice) from a range of foods and drinks.
Satiety index calculated by dividing the area under the satiety response curve for the test food by the mean satiety
AUC for white bread and multiplying by 100.
Fruits ranked at the top with a satiety index 1.7 times more satisfying than white bread (varies with the fruit)
,Blue bar represents the range of reported satiety values
Black line represents the calculated Fullness Factor (regression equation that weighs protein, fat, fibre and energy
density)
Can see that the Fullness Factor does reasonably predict the satiety responses, with possible exception of potatoes.
However, methodology of this study may have contributed to an artificially high satiety value for potatoes: Per the
study's design, the participants were separately fed 220-Calorie servings of each food. A 220-Calorie serving of plain
potatoes is larger and much less palatable than the other foods studied. The size of this serving may have influenced
a repulsion to this test food that goes beyond the normal satiating response.
Limitations of the Fullness Factor:
It is calculated from the food’s nutrient content, using values from those nutrients that have been shown
experimentally to have the greatest impact on satiety. There are, however other things that can influence a food’s
ability to satisfy hunger. For example, its palatability can encourage or discourage consumption → Palatability
cannot be accurately measured because it is highly individual and a subjective value.
Fullness factor by design is an estimate of food satiety prior consumption.
Continuing with Holt et al. (1995)...
Protein (r = 0.37), fibre (r = 0.46), and water (r = 0.64) correlated positively with the Satiety Index.
Fat content negatively associated with Satiety Index (r = -0.43)
Fatty foods are not satisfying.
, Dietary fiber and protein seem to represent the two most potent macronutrients with respect to inducing a satiety
response.
Blundell et al. (1996):
High-fat diets lead to a high energy intake
High-fat foods exert a weak effect on satiation (within meal)
Fat has a weaker effect, joule for joule, on post-ingestive satiety than other macronutrients (between meals)
Obesity is more common among high rather than low-fat consumers.
Ortinau et al. (2014):
Background: The purpose of this study was to determine whether a high-protein afternoon yogurt snack improved
appetite control, satiety, and reduces subsequent food intake compared to other commonly-consumed, energy
dense, high- fat snacks.
20 healthy women completed randomised, crossover study which included 3 8hour testing days.
Participants were acclimated to each snack (high-protein yogurt, high-fat crackers, high-fat chocolate) for 3
consecutive days.
On day 4, consumed standardised breakfast and lunch and the snack was then consumed 3 hours post-lunch.
Perceived hunger and fullness were assessed and an ad libitum dinner was provided.
The consumption of the yogurt snack led to greater reductions in afternoon hunger vs. chocolate. No differences in
afternoon fullness were detected.
The yogurt snack also delayed eating initiation by approximately 30 min compared to the chocolate snack and
approximately 20 min vs. crackers.
The yogurt snack led to approximately 100 fewer kcals consumed at dinner vs. the crackers and chocolate.
No other differences were detected.
These data suggest that, when compared to high-fat snacks, eating less energy dense, high-protein snacks like yogurt
improves appetite control, satiety, and reduces subsequent food intake in healthy women.
World Health Organization (2003): Macronutrients and Obesity
Attention has been increasingly drawn to energy density, the amount of energy per gram of food.
We eat a fairly constant amount of food.
Hence if we eat more energy dense foods, we consume more calories.
The energy density of foods is a key determinant of energy intake.
There is “convincing evidence” that a high intake of high-energy-dense foods is associated with an increased risk of
obesity.
Drewnowski (1998): Energy Density
The major components that determine energy density are water, fat and fibre.
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