![[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}
|
|
|
|
|
||
Masterfoods USA, Vernon, CA 90058
3 To whom correspondence should be addressed. E-Mail: tiffany.bierer{at}effem.com.
KEY WORDS: • dog • weight loss • high protein • conjugated linoleic acid • canine
The number of obese and overweight people is of growing concern in the human population. Estimates of the incidence of obesity of dogs in the United States are as high as 25% of the dog population (1).
Current weight loss regimens for pets often involve a severe calorie restriction that is many times coupled with high intakes of dietary fiber. Either alone or combined with an increase in physical activity, these diets are efficacious when strictly followed. Unfortunately, they are often not followed. In addition to the reduced palatability and increased stool volume commonly associated with high-fiber diets, the strict calorie restriction required for weight loss often leaves an animal hungry. Aggression and begging in a hungry pet stresses the pet owner who will dramatically increase the pet's caloric intake by offering the pet numerous treats in an attempt to decrease the begging and alleviate the owner's concern that the pet remains hungry after a meal.
The use of high-protein, low-carbohydrate weight loss diets for humans has existed for many years. Recently, these types of diets have increased after the publication of books such as Dr. Atkins' New Diet Revolution (2).
Proponents of high-protein, low-carbohydrate diets claim that they increase weight loss by promoting the metabolism of body fat without a reduction in caloric intake. However, a recent review of low-carbohydrate diets correlated the weight loss achieved in humans with an overall reduction in caloric intake not to changes in macronutrient profile alone (3).
Another dietary component that has been studied as an aid for increasing weight loss is conjugated linoleic acid (CLA).4 CLA has been shown in many species to reduce fat mass while helping to maintain lean muscle mass (4).
Although there are several studies on the effects of low-carbohydrate diets in humans (3), there is relatively little information on the effects of these diets in dogs. A recent study in dogs showed a greater loss of body fat and a sparing of lean body mass in dogs fed a high-protein (47.5%), low-carbohydrate weight loss diet than those fed a lower-protein diet (23.8%) when energy intake was severely restricted (5). This current study was designed to examine the effects of feeding a low-carbohydrate/high-protein diet and CLA on promoting weight loss and body composition improvements in dogs with mild caloric restriction.
 |
MATERIALS AND METHODS |
|---|
 TOP MATERIALS AND METHODS RESULTSDISCUSSIONLITERATURE CITED |
|---|
This study was designed as a randomized, controlled trial using 39 overweight, mixed-sex Beagle dogs with body condition scores between 4 and 5 using the following scale: 1, thin; 2, underweight; 3, ideal; 4, overweight; and 5, obese. All feeders, handlers, and data collectors were blinded to the treatments.
Blood chemistry panels (including thyroid panels) and complete blood counts were completed on all dogs before the start of the weight-loss phase. Any dog exhibiting indications of abnormal thyroid, kidney, or liver function was excluded.
Prefeed phase
Before the weight-loss phase of the study, dogs selected for the study went through a prefeeding phase to determine the caloric intake required by the dog to maintain body weight. All dogs were fed the same dry, adult maintenance dog food5 for 5 wk. Body weights were recorded weekly and food intakes were recorded daily. Food amounts offered were adjusted on a per-dog basis to maintain body weight. Water was supplied ad libitum. Any dogs that did not consume the maintenance diet were excluded from the study. At the end of 5 wk, the mean daily caloric intake of each dog was determined for each dog during the last 3 wk of the pretest period. Thirty-nine dogs completed this phase and were included in the weight-loss phase of the study.
Weight-loss phase
All 39 dogs were randomly assigned to one of four test diets: high carbohydrate [control (CON), 28% protein, 43% CHO, 11% fat, n = 10], high carbohydrate + CLA (CLA, 28% protein, 44% CHO, 10% fat, 0.55% CLA, n = 10), high protein (HP, 52% protein, 22% CHO, 8% fat, n = 9), and high protein + CLA (HPCLA, 51% protein, 21% CHO, 9% fat, 0.53% CLA, n = 10)6. The metabolizable energy (ME) of each diet was calculated based on analysis of the diets.
 |
Each dog was fed at 85% of their individual maintenance calories as determined at the end of the prefeed period. Food intakes were measured daily and body weights were measured weekly. Water was offered ad libitum.
Physical examinations were performed by a veterinarian at the start of the weight-loss phase and wk 3, 6, 9, and 12. Blood-chemistry panels and complete blood counts for all dogs were performed at 0, 3, 6, 9, and 12 wk. Blood samples were analyzed by Antech Diagnostics (Memphis, TN). Only 12-wk triglyceride (TG) data is reported in this abstract.
D2O body composition analysis
Body composition analysis using deuterium oxide (D2O) was performed at wk 0 and wk 12 for all groups. D2O was purchased from Cambridge Isotope Laboratories (Andover, MA). On days of body composition analysis, dogs were food deprived overnight and did not consume water for 3 h before testing. Body weight of each dog was recorded and used to calculate the amount of D2O (0.15 g/kg BW) needed for each dog. Blood samples were taken before the administration of the D2O. Once the predosing blood sample was collected, a measured amount of D2O was injected intravenously into each dog. Weights of the syringes and needles before filling, after filling with D2O, and postinjection were all recorded for analysis. Additional blood samples were taken at 2 and 3 h postinjection. All blood samples were taken into lithium-heparin tubes. Plasma was removed, frozen at –70°C, and samples were shipped blinded to Metabolic Solutions (Nashua, NH) for body composition calculations. Data are expressed as the % change of lean body mass (LBM) and fat mass (FM).
Statistical analysis
For each variable, the change from baseline was determined for each dog. These were utilized to calculate the mean for each group, and one-way analysis of variance (ANOVA) by nonequal Tukey's test was used to determine statistical differences among groups at 12 wk. Data are expressed as group means ± SEM. Analysis was done using Excel 97-SR2.
|
RESULTS |
|---|
|
TOPMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
No significant differences were noted among baseline mean body weights (kg) for the CON, CLA, HP, and HPCLA groups (16.63 ± 0.55, 16.79 ± 0.78, 15.55 ± 0.74, and 16.61 ± 0.75, respectively). At 12 wk, the mean body weight loss in the HP and HPCLA groups (–10.9% ± 1.06 and –10.2% ± 2.04) were significantly different from the mean weight loss in the CON group (–4.42% ± 1.11, P < 0.5). The weight loss observed in the HP group was also significantly different from that seen in the CLA group (–4.96% ± 1.78, P < 0.05) (Fig. 1).
|
|
|
|
DISCUSSION |
|---|
|
TOPMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
Despite claims that subjects consuming high-protein, low-carbohydrate diets lose weight with no reduction in calories, recent evidence indicates that the ad libitum consumption of low-carbohydrate diets compared to high-carbohydrate diets is associated with increases in satiety and an overall decrease in total caloric intake (8). In a review of the efficacy of low-carbohydrate diets (3), weight was associated with decreased caloric intake and increased diet duration and not simply with a change in the macronutrient profile of the diet. Low-carbohydrate diets also help stabilize blood glucose levels throughout the day, preventing the hypoglycemia after a high-carbohydrate meal that causes hunger (8,9). This study, however, found no differences in the calories consumed among the groups, whereas the low-carbohydrate groups still lost significantly more weight and fat mass than the high-carbohydrate groups. This suggests that decreased caloric intake is not the sole mechanism of action of low-carbohydrate diets.
Layman et al. (9) observed no difference in weight loss in humans consuming high-carbohydrate diets compared to those consuming low-carbohydrate, high-protein weight loss diets. However, there was a greater loss in fat mass in those subjects on the low-carbohydrate diets. They conclude that substituting carbohydrates for protein in a weight-loss diet induces a greater metabolism of fat than a high-carbohydrate diet. In a study by Johnston et al. (10), substitution of protein for carbohydrate in a low-fat diet was associated with an increase in postprandial thermogenesis. This increase in energy expenditure could help explain the increase loss in body weight and body fat observed with high-protein, low-carbohydrate diets in this study.
Although the CLA group tended to have a greater fat mass loss than the control group, the difference was not significant in this study. In addition, no additive effect of CLA on weight loss or body composition was noted in the group fed CLA in combination with a high-protein diet. These results suggest that the macronutrient change from high-carbohydrate to high-protein content has a greater effect on increasing weight loss than does the addition of CLA to a diet.
This study evaluated the benefits of high-protein, low-carbohydrate diets as well as CLA addition on reducing body weight in dogs. Changing the macronutrient profile of a canine weight-loss diet from a high-carbohydrate level to one primarily based on protein can promote greater weight loss without further reductions in caloric intake. This weight loss is driven primarily from an increased loss of fat mass while maintaining lean muscle mass.
|
FOOTNOTES |
|---|
2 Study sponsored by Masterfoods USA, Vernon, CA.
4 Abbreviations used: BUN, blood urea nitrogen; CHO, carbohydrate; CLA, conjugated linoleic acid; CON, control; D2O, deuterium oxide; FM, fat mass; HP, high protein; LBM, lean body mass; TG, triglycerides.
5 PEDIGREE MEALTIME® Small Crunchy Bites
6 All diets were based on whole corn, corn gluten meal, and chicken by-product meal recipes with the addition of soy protein isolate in the high-protein diets to increase protein levels.
|
LITERATURE CITED |
|---|
|
TOPMATERIALS AND METHODSRESULTSDISCUSSIONLITERATURE CITED |
|---|
1. Armstrong, P. J. & Lund, E. M. (1996) Changes in body composition and energy balance with aging. Vet. Clin. Nutr. 3: 83–87.
2. Atkins, R. C. (1998) Dr. Atkins' New Diet Revolution. Avon Books, New York, NY.
3. Bravata, D. M., Sanders, L., Huang, J., Krumholz, H. M., Olkin, I., Gardner, C. D. & Bravata, D. M. (2003) Efficacy and safety of low-carbohydrate diets. A systemic review. JAMA 289: 1837–1850.
4. DeLany, J. P. & West, D. B. (2000) Changes in body composition with conjugated linoleic acid. J. Am. Coll. Nutr. 19: 487S–493S.
5. Diez, M., Nguyen, P., Jeusette, I., Devois, C., Istasse, L. & Biourge, V. (2002) Weight loss in obese dogs: evaluation of a high-protein, low-carbohydrate diet. J. Nutr. 132: 1685S–1687S.
6. Samaha, F. F., Iqbal, N., Seshadri, P., Chicano, K. L., Daily, D. D., McGrory, J., Williams, T., Williams, M., Gracely, E. J. & Stern, L. (2003) A low-carbohydrate as compared with a low-fat diet in severe obesity. N. Engl. J. Med. 348: 2074–2081.
7. Foster, G. D., Wyatt, H. R., Hill, J. O., McGuckin, B. G., Brill, C., Mohammed, B. S., Szapary, P. O., Radar, D. J., Edman, J. S. & Klein, S. (2003) A randomized trial of a low-carbohydrate diet for obesity. N. Engl. J. Med. 348: 2082–2090.
8. Layman, D. K., Shiue, S., Sather, C., Erickson, D. J. & Baum, J. (2003) Increased dietary protein modifies glucose and insulin homeostasis in adult women during weight loss. J. Nutr. 133: 405–410.
9. Layman, D. K., Boileau, R. A., Erickson, D. J., Painter, J. E., Shiue, H., Sather, C. & Christou, D. D. (2003) A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. J. Nutr. 133: 411–417.
10. Johnston, C. S., Day, C. S. & Swan, P. D. (2002) Postprandial thermogenesis is increased 100% on a high-protein, low-fat diet versus a high-carbohydrate, low-fat diet in healthy, young women. J. Am. Coll. Nutr. 21: 55–61.
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
