![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
|
|
|
|
|
||
WALTHAM Centre for Pet Nutrition, Waltham-on-the-Wolds, Melton Mowbray, LE14 4RT, UK
4 To whom correspondence should be addressed. E-mail: penelope.morris{at}eu.effem.com.
KEY WORDS: • intake • energy density • feline • regulation
Whether mammals have the ability to regulate total intake or intake of specific macronutrients is controversial. The definition of an animal that can regulate is one that will alter its ingestive behavior to maintain ("defend") adequate nutrient intake (1). Locusts, for example, alter the volume ingested to maintain intake of protein and carbohydrate in the face of dilution of foods with nondigestible bulk, a range of macronutrient combinations, or variation in the frequency of, and differing distances between macronutrients (1). Another striking example comes from the work of Theall et al. (2). In those experiments, rats ingested amounts of protein and carbohydrate within a tight range when challenged with foods containing 8 different macronutrient combinations. Rapid compensation for dietary dilution was also observed in many omnivorous and herbivorous species such as chickens (3), horses (4), cows (5), and humans (6).
Anecdotally, it was believed that cats were also able to regulate intake to maintain adequate macronutrient and energy intake. Small-scale studies suggested that cats consuming feed ad libitum will eventually reach a stable energy intake, but the weight at which this occurs is not predictable (7). This has important implications for feline health because the incidence of obesity is estimated at 
25% (8) and is predicted to rise. If cats merely regulate to the volume eaten, then a potential solution to obesity is the production of less energy-dense foods. If cats regulate to energy or macronutrient target, however, this approach will be unsuccessful. Previous studies were conducted over short periods and without adequate power, making it difficult to draw firm conclusions (9–12). The aim of the current study was to examine the effect of dietary dilution on intake in a large population of cats over an extended period of time.
 |
MATERIALS AND METHODS |
|---|
 TOP MATERIALS AND METHODS RESULTSDISCUSSIONLITERATURE CITED |
|---|
|
Data were assessed for normality of distribution by the Kolmogorov-Smirnov test. A paired sample t test was used to assess changes in body composition at the beginning and end of each trial phase. Changes in intake and body weight were assessed for significance using analysis of repeated measures. All statistical analyses were conducted using SPSS v 13.0. Differences were considered significant when P 
0.05. Data are presented as means ± SD, unless stated otherwise.
|
RESULTS |
|---|
|
TOPMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
When cats were fed Diet C, there was a significant reduction in energy intake within the first 5 d of exposure to the diet (P = 0.050; Fig. 1). A similar, if less pronounced change in energy intake was observed when cats first started to eat Diet B. However, when the mean weekly energy intake was compared, this did not vary significantly over time with either diet (Diet B wk 1, 180 ± 48 kcal, wk 10, 190 ± 50.59 kcal, P = 0.899; Diet C, wk 1, 250 ± 73 kcal, wk 10, 232 ± 70 kcal, P = 0.939). The mean energy intake, however, was significantly different between trial diets at all time points (P = < 0.001) with cats consuming more calories when fed the higher energy density diet, Diet C. This was consistent on an individual cat basis with 22 of the 26 cats ingesting significantly more calories when fed Diet C (P = <0.01), whereas changes in energy density did not significantly alter energy intake in 4 cats.
|
|
|
DISCUSSION |
|---|
|
TOPMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
For the remaining cats, energy intake did not differ over time with consumption of either Diet B or Diet C, but when cats ate Diet C, the more energy-dense food, they consumed more calories than when they were fed Diet B. Goggin et al. (7) previously showed in a small number of cats, in caged housing, that any compensation for reduced energy density requires a long period of time (80 d), and the weight at which a cat stabilizes is extremely variable. Other studies showed that adaptation to reduced energy density diets can take between 75 and 200 d (13) before cats return to eating a volume of food sufficient to maintain their energy requirements. The current study showed that over a 10-wk period, there was no adaptation to altered energy density in terms of either energy intake or body weight in all but 4 of the cats. Although these data agree with the findings of Goggin et al. (7), our data are significant in that they were obtained in cats that lived in an environment typical of that of apartment or indoor cats. Many cats throughout the world live solely indoors, and it is in this population of cats that the incidence of obesity is particularly high.
The data obtained in this study show that cats ate approximately the same amount of food (g/kg body weight) irrespective of which diet they were given. This resulted in a higher energy intake when the cats ate Diet C, the more energy dense of the 2 diets. Some cats gained weight, which can be explained by the availability of excess energy. Nine cats however, maintained their body weight within 5% of their starting weight while consuming Diet C. Four of these cats were able to maintain their body weight irrespective of which diet they ate; the remaining 5 cats lost weight while consuming the energy-diluted diet, Diet B. All cats either maintained or lost weight while consuming Diet B, despite excess food being available. It is possible that the cats that lost weight were not able to increase their energy intake due to limits in gut distension. All cats were meal fed, which may have limited the opportunity for some cats to eat throughout the day to reach their energy requirements and therefore maintain body weight.
The changes in body composition did not reflect the changes in body weight. Nine of the 26 cats gained body fat, measured in grams, when fed the less energy-dense diet, Diet B, whereas none of the cats gained body weight while consuming this diet. This reflects a disproportionate loss of lean body mass and highlights the importance of including body composition measurements in future studies. The aim of any weight loss program should be to maximize loss of fat while minimizing loss of lean tissue. Preventing the loss of lean tissue minimizes weight loss–induced suppression of metabolic rate (14) and prevents weight regain.
In all but a minority of animals in this study, cats appeared unable to self-regulate their energy intake when fed commercial wet diets. The data suggest, however, that stomach fill may play an important role in constraining food intake in cats that are meal fed. For overweight cats, feeding an energy-dilute wet diet in 2 discrete hourly meals may be one way of either minimizing further weight gain or promoting slow weight loss. The diet, however, should be suitably balanced to ensure that the cat receives the optimum level of essential nutrients, and that the weight loss results from fat loss and is not so rapid that complications arise.
|
FOOTNOTES |
|---|
2 Author disclosure: no relationships to disclose.
3 This work was supported by the WALTHAM Centre for Pet Nutrition.
|
LITERATURE CITED |
|---|
|
TOPMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
1. Simpson SJ, Batley R, Raubenheimer D. Geometric analysis of macronutrient intake in humans: the power of protein? Appetite. 2003;41:123–40.[Medline]
2. Theall CL, Wurtman JJ, Wurtman RJ. Self-selection and regulation of protein and carbohydrate ratios in foods adult rats eat. J Nutr. 1984;114:711–8.
3. Hill FW, Dansky LM. Studies on the energy requirements of chickens, 1. The effect of dietary energy level on growth and feed consumption. Poult Sci. 1954;33:112–9.
4. Laut JE, Houpt KA, Hintz HF, Houpt TR. The effects of caloric dilution on meal patterns and food intake of ponies. Physiol Behav. 1985;35:549–54.[Medline]
5. Baile CA, Forbes JM. Control of feed intake and regulation of energy balance in ruminants. Physiol Rev. 1974;54:160–214.
6. Speigel TA. Caloric regulation of food intake in man. J Comp Physiol Psychol. 1973;84:24–37.[Medline]
7. Goggin JM, Schryver HF, Hintz HF. The effects of ad libitum feeding and caloric dilution on the domestic cat's ability to maintain energy balance. Feline Pract. 1993;21:7–11.
8. Donoghue S, Scarlett JM. Diet and feline obesity. J Nutr. 1998;128:2776S–8.
9. Castonguay TW. Dietary dilution and intake in the cat. Physiol Behav. 1981;27:547–9.[Medline]
10. Hirsch E, Dubose C, Jacobs HL. Dietary control of food intake in cats. Physiol Behav. 1976;20:287–95.
11. Kanarek RB. Availability and caloric density of the diet as determinants of meal patterns in cats. Physiol Behav. 1975;15:611–8.
12. Rowland N. Glucoregulatory feeding in cats. Physiol Behav. 1981;26:901–3.[Medline]
13. Skultety FM. Alterations of caloric intake in cats following lesions of the hypothalamus and midbrain. Ann N Y Acad Sci. 1969;157:861–74.[Medline]
14. Stefanick ML. Exercise and weight control. Exerc Sport Sci Rev. 1993;21:363–96.[Medline]
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
