Effects of dietary fatty acids and exercise on body-weight regulation and metabolism in rats.

OBJECTIVE

To assess the interaction of high-fat diets (HF) made with different dietary fatty acids and exercise on body-weight regulation, adiposity, and metabolism.

RESEARCH METHODS AND PROCEDURES

Male Wistar rats born to dams fed HF diets (40% w/w) made with either fish oil (FO), soybean oil (SO), or palm oil (PO) were fed diets similar to their dams and divided randomly into exercise (EX, swimming) or sedentary control (SD) groups when they were 9 weeks old. EX lasted for 6 weeks. Twenty-four hours after the last EX bout, fasted rats were killed by decapitation. Chemical analyses and body composition analysis were conducted.

RESULTS

The results demonstrated that different fatty acids had different effects on body weight, composition, and metabolism. SO-fed rats gained the most weight and fat. EX reduced body weight of FO- and PO-fed rats, but SO-fed rats were still heavier and fatter than other rats. Data from SO- and PO-fed rats suggested that they are insulin resistant and that EX normalized this abnormality. Of the three HF diets used, FO produced the least adverse effects compared with PO and SO.

DISCUSSION

Not only the quantity of dietary fat, but also the type of fat used, will produce different effects on body weight and metabolism. EX ameliorates the suggested insulin resistance induced in rats fed either highly saturated or n-6 polyunsaturated fatty acids. Long-chain n-3 polyunsaturated fatty acids, as found in fish oil, are more beneficial than n-6 polyunsaturated fatty acids when fed in high amounts to rats.