Low-protein diet blocks development of hyperphagia and obesity in rats with hypothalamic knife cuts.

The objective of this study was to examine the influence of dietary protein levels on development of hyperphagia and obesity in rats that had been given surgical knife cuts between the ventromedial and lateral areas of the hypothalamus. Under normal conditions, rats with this type of surgery exhibit hyperphagia and become obese when given unlimited access to dietary energy. Earlier studies indicated impaired adaptive diet-induced thermogenesis in response to excess energy intake in this animal model of obesity. Because low protein diets can also stimulate diet-induced thermogenesis, we conducted four experiments which examined how diets containing different levels of protein affect development of hyperphagia and obesity in female rats given bilateral, parasagittal wire knife cuts between the ventromedial and lateral areas of the hypothalamus. For 28 d, knife-cut and sham-operated rats were given unlimited or restricted (1 79 or 1 80 kJ/d) access to diets containing protein at 5, 10 or 20% of total metabolizable energy. Knife-cut rats with unlimited access to 10 or 20% protein diets became obese, gaining 2-3 times more weight and 3-6 times more carcass energy while consuming 55-89% more energy than sham-operated rats. In contrast, energy consumed and gained by knife-cut rats with unlimited access to a 5% protein diet was similar to that of rats given sham surgery. Results indicate that a low protein diet effectively blocks development of hyperphagia and obesity in rats with surgical knife cuts between the ventromedial and lateral regions of the hypothalamus.

An analysis of excessive running in the development of activity anorexia.

Food restriction combined with activity wheel access produces activity anorexia: a combination of excessive running, reduced food intake and rapid weight loss. Temporal distributions of running in activity anorexia were examined in a reversal design with one of 2 x 2 x 2 factorial combinations (pelleted-vs-powdered food x deprivation x wheel access) as the treatment condition. Wheel revolutions were recorded in 30 min intervals; body weights, food and water intakes were measured daily. Only wheel access combined with food deprivation reliably produced activity anorexia. Excessive running occurred in the absence of schedule-induced polydipsia, was unaffected by food form, and showed distributional characteristics of facultative behavior. These results are inconsistent with schedule-induced behavior explanations. Running distributions appeared consistent with chronobiological models with light/dark onset and feeding serving as zeitgebers.

Muscle fibre size and number following immobilisation atrophy.

Muscle fibre number and cross sectional area were studied in the response to immobilisation atrophy of the long head of the triceps brachii. Following eight weeks of immobilisation, fibre number of the muscle from the immobilised limb was compared to that of the contralateral control limb in six rats. Mean fibre cross sectional area of the LHT from the immobilised limb was compared to that of the contralateral control for another six animals. Atrophy, as estimated by a decrease in wet muscle weight, was 38.0% for the group used for fibre number estimations and 45.7% for the group used for fibre area. Fibre counts revealed no difference between muscles from immobilised and control limbs. Mean fibre area was 42.1% less for the muscle from the immobilised limb compared to the control limb. The results of this study indicate that atrophy of the LHT produced by immobilisation of the forelimb is the result of atrophy of the muscle fibres without a decrease in muscle fibre number.

Effects of a behavioral weight-loss program food purchases: instructions to shop with a list.

Effects of instructions to shop with a list on subsequent food purchases were evaluated in the context of a 12-week behavioral/nutritional weight loss program. In the fifth class, subjects were taught to prepare a weekly menu, convert the menu to a shopping list, adjust the list for foods already on hand and organize the list to be consistent with supermarket layout. Subjects were told to attempt to restrict their purchases to items and amounts on the list. Food purchases were reduced from 16,188 kcal per person per week prior to the shopping class to 9625 kcal during the remainder of the treatment period in five subjects losing greater than or equal to 4.5 kg during treatment and from 14,620 kcal to 12,305 kcal for five subjects losing less than 4.5 kg during the treatment. The decrease for subjects losing less than 4.5 kg did not reach significance, but a further decrease to 10,254 kcal during follow-up was significantly less than pre-intervention purchases. Reductions posted by the greater than or equal to 4.5 kg subjects were maintained over a 12-week post-treatment follow-up period. A non-equivalent control group of six shoppers who were not attempting to lose weight did not change over the same time period, (averaging 14,470, 14,939 and 12,636 kcal at pre-intervention, post-intervention and follow-up respectively), ruling out seasonal factors as an alternative explanation. Food purchases were also analyzed for qualitative changes.

Relationship of hunger, use of a shopping list and obesity to food purchases.

Shopping with a list and shopping after a meal are two commonly employed behavioral weight loss guidelines designed to reduce food purchases and therefore food consumption. A survey of 596 female shoppers, which analyzed purchases on the basis of caloric value, failed to support either of these guidelines. Analysis of kilocalories (kcal) purchased indicated that overweight shoppers purchased more total kcal, with a greater percentage of their kcal coming from fat and correspondingly lower percentage of kcal coming from carbohydrates.