Appetite dysfunction in obese males: evidence for role of hyperinsulinaemia in passive overconsumption with a high fat diet.
OBJECTIVE
To test the hypothesis that caloric and fat intake in a pre-load meal have no subsequent effects upon blood glucose and insulin concentrations, perceived hunger, subsequent food intake and appetite control in lean and obese men.


METHODS
Lean and obese men reported to the laboratory in the morning in a fasted state where they were subject to an eating test based on the pre-load-test meal paradigm, using a double-blind protocol. The breakfast pre-load was either a reduced caloric low-fat (LF) meal or an overfeeding high-fat (HF) meal. LF was 20% of each individual's average daily energy requirement (ADER) and comprised 60% carbohydrate, 27% protein, and 13% fat, whilst HF was adjusted to yield 55% of the ADER, and comprised 45% carbohydrate, 22% protein and 43% fat. The pre-loads on both trials were administered as one single mean, and were given in a random order. After 5(1/2) h, an ad libitum test-lunch was given to determine how much energy was consumed. Between the two meals, blood samples were collected and subjective hunger ratings were assessed hourly. These variables were measured at 30-min intervals for 75 min after the ad libitum meal.


METHODS
Twelve healthy men, six of whom were lean (BMI 22. 50+/-1.08 kg.m2) and six of whom were obese (BMI 39.05+/-11.63 kg. m2) were recruited.


RESULTS
When given 55% of their ADER in a HF pre-load meal, the obese group consumed more energy (5426+/-1126 kJ; F1,20=11.45, P<0.01), than the lean group did (3473+/-1114 kJ), accounting for 45% of the ADER in that meal setting. However, no differences between lean and obese intake were noted at the test meal following a LF pre-load. The lean group exhibited a significant inverse correlation (r=0.628, P<0.05) between serum insulin concentration before eating the test meal and the amount of energy consumed at the test meal, while such a relationship was absent in the obese group.


CONCLUSIONS
The obese males were unable to compensate for the caloric overloading when fed a HF (55% ADER) pre-load at a subsequent test meal, whereas a calorically reduced pre-load (20% ADER) produced similar intakes to the lean control group. The inverse relationship noted in the lean group between insulin levels before the test meal and the energy intake at that test meal suggests that insulin may play a role in the regulation of appetite - satiety mechanism in lean males. The absence of such a relationship in the obese may suggest the site for possible appetite dysfunction contributing to obesity. These results further suggest that when obese individuals consume a high-fat meal they are prone to passive overconsumption, whereas lean study participants appear to be more resistant to such a phenomenon.
Speechly
D P
DP
Department of Physiology, University of the Witwatersrand Medical School, 7 York Road, Parktown, 2193, Johannesburg, South Africa. david_p.speechly@virgin.net
Buffenstein
R
R
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001824:Body Constitution; D015992:Body Mass Index; D001835:Body Weight; D004041:Dietary Fats / Q000008:administration & dosage*; D002149:Energy Intake; D005502:Food; D006801:Humans; D006815:Hunger; D006946:Hyperinsulinism / Q000150:complications*; D006963:Hyperphagia / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*
D001786:Blood Glucose; D004041:Dietary Fats