Food Lipids: Chemistry, Nutrition, and Biotechnology

For example, some have reported that males who are of normal weight and not
concerned about their body weight or food intake (‘‘unrestrained eaters’’) appear to
compensate adequately for the caloric content of a preload (24). Porrini et al. (31)
report that a high-protein food given as a snack 2 hours before a meal exerts a higher
effect on both intrameal satiation and postingestive satiety than a high-fat snack.
When a first course is consumed as part of a meal, the sensory characteristics of the
foods play an important role in controlling subsequent food intake. Others (20) have
shown that in obese individuals, fat exerts only a weak action on satiety. Data such
as these have led to the speculation that obesity may be the result of an insensitivity
to satiety signals generated by ingestion of fat.
In studies of satiation, dietary fat is an integral variable of the test diet(s).
Studies show that caloric intake is greater with dietary fat than with carbohydrate.
When subjects are fed diets in which fat, fiber, and simple sugars are manipulated
to obtain low energy versus high energy diets, energy intake is greater on the high
energy as compared with the low energy diet (32). Caputo and Mattes (33) reported
that individuals consuming high-fat meals consume more calories than those consuming
high- or low-carbohydrate or low-fat meals. Others (34) have shown that
individuals consuming high-fat or high-carbohydrate diets for 1 week consume more
calories on the high-fat versus high-carbohydrate diets. This hyperphagic effect of
dietary fat has been observed in many studies (35–39).
The excessive intake of dietary fat primarily occurs during a meal to increase
meal size rather than between meals to increase meal frequency (37). Overconsumption
is particularly high when fat is combined with alcohol (40). Over the long
term, many investigators have shown that this passive overconsumption of dietary
fat can lead to obesity [for review, see (37,41)].
Relatively few long-term studies on humans have been conducted because of
difficulties such as inability of the investigator to control for the subjects’ current or
past food intake, activity level, or genetic background. However, Kendall et al. (11)
reported that women consuming either a low- or high-fat diet for two separate 11week
periods consume more calories on the high-fat diet. Lissner et al. (10) also
showed that subjects eating either a low-, medium-, or high-fat diet for 2 weeks
consume the most calories on the high-fat diet.
In addition, animal studies have shown that the type of fat may influence the
satiation effects of dietary fat. In both chickens (42) and rats (43), medium chain
triglycerides have been shown to have a greater satiating effect than long chain
triglycerides. Rolls (44) and Stubbs (45) both report that in humans, substitution of
long chain triglycerides with medium chain triglycerides depresses food intake. Also,
the physical form as well as the type of fat contributes to its satiation effects (27,46).
Overeating occurs with diets containing saturated fats (47–50) as well as mixed fats
(51–54). Recently, Lawton et al. (55) showed that in human subjects polyunsaturated
fatty acids may exert a stronger control over appetite than monounsaturated or saturated
fatty acids.
Some have suggested that the hyperphagic effect of high-fat diets is not due
solely to the fat but is influenced by the presence of carbohydrate and overall caloric
density (56). Ramirez et al. (56) fed rats diets varying in carbohydrate, fat, cellulose,
or caloric density and found that energy intake varies directly as a function of caloric
density regardless of the fat or cellulose content of the diets. They concluded that
high levels of fat, carbohydrate, and energy interact to produce overeating in animals
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