OBJECTIVE To investigate whether a controlled physical training plan for overweight dogs during a weight loss program would improve cardiorespiratory fitness and better preserve lean body mass, compared with results for dogs undergoing a weight loss program based on caloric restriction alone.
DESIGN Prospective, nonrandomized clinical study.
ANIMALS 19 client-owned overweight or obese dogs.
PROCEDURES All dogs were fed the same calorie-restricted diet rationed to achieve a weight loss rate of 1% to 2%/wk for 12 weeks. The fitness-and-diet (FD) group participated in a training program that included underwater and land-based treadmill exercise 3 times/wk. The diet-only (DO) group had no change in exercise routines. Daily activity before and during the intervention was recorded by accelerometry. Before and after intervention, heart rate during exercise was recorded to assess cardiovascular fitness, and body composition was analyzed by dual-energy x-ray absorptiometry. Differences between groups were evaluated with t tests and multiple regression analysis.
RESULTS Mean weight loss was 13.9% and 12.9% for the FD and DO groups, respectively (n = 8 dogs/group that completed the study). Mean accelerometer counts during intervention were 13% higher than baseline counts for the FD group. Heart rate during exercise declined after intervention in both groups. Lean body mass was preserved in the FD group and lost in the DO group during intervention.
CONCLUSIONS AND CLINICAL RELEVANCE The controlled exercise plan used with a dietary weight loss program prevented loss of lean body mass in dogs. This finding supports inclusion of controlled physical training for obesity management in dogs.
Excess body weight is a frequently observed problem in the canine population.1,2 Overweight and obese dogs have a shorter life span, reduced quality of life, and increased risk of diseases such as degenerative joint disease and neoplasia, compared with nonoverweight dogs.3 Similar to findings reported for people, adiposity in dogs results in numerous metabolic changes, such as insulin resistance, hyperlipidemia, and chronic low-grade inflammation.4,5 Obesity research in human patients emphasizes the healthpromoting effects of physical activity,6 but to date, the value of physical activity has received little attention in canine obesity research. Increased physical activity is often recommended as an adjunct to restricted energy intake in weight loss programs for dogs,4,7 but scientific studies evaluating the effects of such a regimen are scarce and lack documentation of the successful accomplishment of increased physical activity during the programs.
During the last decade, pedometers and triaxial accelerometers have been validated for use in dogs as reliable ways to record the number of steps taken (pedometers) or movement (accelerometers), making it possible to monitor a dog's activity level in its home environment8–10 and during treadmill activity.11 These tools are useful for quantifying physical activity in canine obesity and fitness research. Studies have reported fewer steps12 and less vigorous physical activity13 by overweight dogs, compared with normal-weight dogs; however, in 1 study,14 overweight dogs did not spontaneously increase their physical activity during a 6-month weight loss program, despite successful weight loss.
For physical activity to have optimal health benefits in people, it should be linked to improved cardiorespiratory fitness.15 Heart rate during exercise has been used to assess fitness in several canine exercise studies, but research has so far focused on fit dogs under strenuous exercise.16–18 The effect of weight loss and exercise on heart rate in overweight pet dogs has only been sparingly studied.19
Weight loss usually results in loss of both fat and lean body mass. Factors affecting lean body mass loss during canine weight loss programs include protein content in the diet and weight loss rate. A high-protein diet has been reported to reduce the loss of lean body mass in dogs to a ratio of 15% to 20% of the total loss,20,21 compared with 30% when a moderate-protein diet was fed.21 Results of studies22,23 in people have shown that loss of lean body mass can be prevented or minimized, if weight loss is obtained by use of a low-calorie, high-protein diet in combination with physical exercise. Preservation of lean body mass is preferable because it preserves energy requirements and physical strength, and thereby the achieved weight loss is easier to maintain than that achieved by dietary changes alone.24,25
The purpose of the study reported here was to investigate whether a controlled exercise program for overweight dogs during a weight loss program would improve measures of cardiorespiratory fitness (as determined by heart rate during exercise) and better preserve lean body mass (as measured by dual-energy x-ray absorptiometry), compared with results for dogs undergoing a weight loss program based on caloric restriction alone. We hypothesized that dogs having exercise added to the weight loss program would have a lower heart rate during exercise, compared with the preintervention value, and lesser loss of lean body mass, compared with that for dogs undergoing caloric restriction alone.