Letters: A reader's perspective on weight loss
Biological energy efficiency adaptations undermine the rate of weight loss and successful weight maintenance.1,2 Dogs with successful weight loss can regain their pre-diet weight with 40% fewer calories in less time than initial obesity induction.3 A recent long-term follow-up study of dogs that had successfully lost weight found 48% had regained weight in the follow-up period.4 Studies in human energetics confirm the same conclusion: evolution has favored adaptations for energy conservation and weight regain. Biological mechanisms to promote weight loss are nonexistent.
Studies of energy efficiency dynamics during and after dieting are lacking in dogs and cats. Studies in people and rats confirm that food energy density can influence weight maintenance after calorie restriction.5,6 Recent studies in cats document this effect by using water to decrease energy density.7,8 Studies in dogs suggest that feeding a reduced-density, high-protein and high-fiber diet may aid in attenuating weight regain post-dieting.4,9The importance of exercise during and after weight loss has been extensively studied in people. Regular exercise attenuates the metabolic efficiencies associated with weight loss by enhancing fat thermogenesis.10 Surprisingly small amounts of energy expenditure are necessary to aid weight maintenance. A recent one-year follow-up study concluded that as little as 80 minutes of weekly aerobic or resistance training had positive effects on preventing weight regain in people.11 Again, studies in dogs and cats are lacking. Similarities in evolutionary forces would suggest that exercise heavily influenced energy adaptations in early canids.
As predators and scavengers, people and dogs had vast forage areas that required large expenditures of energy. Estimates of daily energy expenditures in Neanderthals are 3,000 to 5,500 kcal/day.12 This heavy expenditure coupled with infrequent meals has resulted in a tremendous evolutionary capacity to store and conserve energy.13 Faced with adequate to excessive caloric intake, dogs can ill afford 60% to 80% of their day spent lying down or sleeping.14
Despite a different hunting solution, evolutionary forces also favored energy efficiency in felids. Consuming smaller prey (the average mouse contains about 30 kcal) coupled with variable hunting success required activity levels that influenced energy conservation adaptations and far exceeded the exercise activity of their modern kin. Although more research is needed in this area to specifically define the role and quantity of exercise in pet weight loss and maintenance, weight loss programs should stress appropriate exercise regimens.
What does all of this research mean for practices offering weight loss programs? Supervision of weight loss is paramount. A vigorous commitment to weight rechecks provides opportunities to make caloric adjustments to periodic efficiency adaptations during dieting (plateaus) and reassure owners that weight loss is a complex, nonlinear process. Exercise recommendations with monitoring (pet pedometers) stress a necessary, total lifestyle change for weight loss and maintenance. Exit consultations after successful weight loss need to emphasize low-density food choices and strict adherence to caloric intake recommendations. Vegetable and fruit treats and rewards can be substituted for calorie-dense treats. Quarterly or triannual fitness evaluations allow early intervention, especially in obesity-prone breeds or individual pets.
Pet weight management is a chronic challenge requiring the same commitment as that given to patients with chronic kidney disease, cardiac insufficiencies, diabetes mellitus, and hypertension. Weight management solutions need to be comprehensive with a long-term perspective.
Ken Tudor, DVM, member, American Academy of Veterinary Nutrition