Facts & Fiction of Weight Loss Programs for Dogs & Cats
ACVIM 2008
Iveta Becvarova, DVM, MS, DACVN
Blacksburg, VA, USA


Successful weight loss programs for companion animals consist of a customized weight loss plan, owner's commitment and regular rechecks. Over the decades, a variety of weight loss strategies have been developed, including therapeutic diets, drug interventions, and non-therapeutic options. However, evidence of effectiveness is often lacking or is highly variable. This presentation will focus on a critical evaluation of the evidence supporting various aspects of obesity management.

What Was the Owner's Compliance in Weight Loss Clinical Trials?

The approach to the owner appears to be a critical aspect in establishing their commitment to the pet's weight loss. The owner should be motivated by having a good understanding of the detrimental effects of obesity particularly its effect on overall health and longevity of their pet. Even the best weight loss program will not work without the owner's compliance. In a study by Butterwick et al 2/32 (6%) of owners did not return after initial consultation.1 Gentry reported that 5/20 dogs (25%) and 3/8 cats (38%) that started on the weight loss program, did not complete the study.2 Poor owner compliance resulted in a drop-rate of 15/60 dogs (25%) in Yaissle's study.3 Remillard published that in a group of self-motivated owners, 56% of dog owners and 54% of cat owners did not return for checkup visits and abandoned the program in the month following the first visit.4 A recent weight-loss clinical trial revealed that 17 out of 19 (89%) participating owners did not comply with the feeding protocol, with 16/17 owners giving treats and 12/17 dogs stealing food.5 These drop rates are similar to the compliance in human weight loss trials. A weight loss trial including 60,164 men and women who ate prepackaged prepared food items, received counseling on making food choices and attended weekly meetings with consultants resulted in increasing drop-rates of 27% after 4 weeks, 58% at 13 weeks, 78% at 26 weeks and 93.4% at 52 weeks of the study.6

The strategies that may improve owner's compliance include providing incentives such as giving the food at no cost to the client or financial rewards, one-time fee for a limited time-period, taking pictures of the pet prior and after weight loss, achieving detectable weight loss rates of 1-2% body weight (BW)/week and making the clinic scale available between rechecks.

Does Owner Education Result in Higher Weight Loss Rates of the Pet?

The applications of behavioral principles to the treatment of obesity in humans are well-developed, which implies that similar strategies could apply to owners of obese pets. Surprisingly, no difference in weight loss rates was found between a group of dogs on a conventional weight loss program and the same weight loss program enhanced with client education through classes on canine obesity topics.3 In this study, mean weight loss of 15% of BW, decrease in Body Condition Score (BCS) by 2 points on a 9-point scale in 6 months and maintenance of this new weight for 18 months were achieved in all dogs. The inclusion of owner education did not affect the ability of the pet to lose weight or maintain weight after weight loss, suggesting that an intense behavior change approach to obesity treatment was not necessary for success. However, there was no continuation of weight checks after the study to determine whether dogs maintained their weight without monthly rechecks.

How Much to Restrict the Pet's Energy Intake to Achieve Adequate Weight Loss Rates in Clinical Practice?

The objective of a successful weight loss program is to achieve a loss of 1-2% of the initial BW per week, or 4-8% per month. Various experimental trials including colony dogs and cats report weight loss rates of 1.3-2.6% of initial BW per week.7-9 However, when these energy restriction rates were applied in clinical trials with client owned animals, weight loss rates were markedly lower, ranging from 0.38 to 0.85% of initial BW per week (Table 1). There are many possible reasons for slower weight loss rates in client owned animals including different age, sex, neuter status, level of exercise, various ambient temperature and approximately 20% lower maintenance energy requirement (MER) compared to colony dogs. Although unproven, a likely important issue is the underreported compliance by the owner with the dietary protocol, which is difficult to measure in clinical trials.5 Furthermore, there is an evidence of breed differences with Labradors requiring greater level of energy restriction than Beagles.10 These results indicate that in order to achieve desired weight loss rates in client owned animals, energy restriction could be more severe.

How Much Energy Restriction Is Too Much?

It is not uncommon that energy consumption of an overweight/obese dog or cat is already lower than 60% of MER without obvious weight loss. In these situations, it is recommended to confirm the diet history and decrease the current energy intake by 20%. When energy restriction becomes too severe it may negatively affect the animal's behavior and overall health. Small breed male dogs consuming 50% MER showed decreased overall activity during the period of restricted caloric intake, and increased focused barking and aggression during the first day of energy restriction.11 In addition to the changes in behavior, sudden loss of weight may cause exaggerated muscle mass loss, as reported in humans.12 Decreased physical activity and loss of lean muscle mass can actually be counter-productive, leading to a lowered energy expenditure and resting metabolic rate.7 Furthermore dogs, like humans, experience a weight rebound following caloric restriction.13 In an experimental study, the weight gain after the end of a weight loss period was more intense and faster in dogs with a more severe level of energy restriction. The group of dogs that best maintained the new reduced body weight was losing at an average rate of 1.14% of BW weekly. This data suggest that gradual weight loss should provide the best chance for long-term success.

In experimental conditions with cats, a rate of ~1% BW loss per week was achieved by feeding 60% of MER calculated for the target BW (36 kcal/kg target BW/day).14 This resulted in the majority of weight loss from body fat (90%) and minimal loss of lean body tissue (8%). While energy restriction to the degree of 45% of MER at target BW proved safe in cats, it resulted in an increase in the proportion of weight loss from lean body mass (19%), and a relative decrease in the proportion of weight loss from body fat (80%). Thus, energy restriction below 60% of MER for target body weight may have an undesirable effect on body composition in cats.

Table 1. Weight loss clinical trials conducted on obese dogs and cats.




energy intakes

Weight loss
% IWa/week

Control of


22 cats

Not reported

18 wks

60% of MER for target BW
(48 kcal/kg target BW)


Questionnaire (recording amount eaten daily)

Butterwick et al, 19941

5 cats

Mean 80% (28-125%)

Mean 27 wks

Mean 43 kcal/kg target BW

Mean 0.78%


Gentry, 19932

15 dogs

Mean 50% (24-77%)

Mean 24 wks

60% of MER (MER = 132 x BWkg0.75) target BW
[79.2 x BWkg0.75]

Mean 0.38%


Gentry, 19932

19 dogs

Mean 22.4%

Mean 177 days

50-82% MER (MER = 105 x BWkg0.75)
[52.5-86.1 x BWkg0.75]

Mean 0.85%

Diary including treats and stolen food

German et al, 20075

13 dogs

Not reported

4 months

50% of MER (MER = 132 x BWkg0.67) target BW
[79.2 x BWkg0.67]



Remillard, 20004

a. IW: Initial Body Weight

Is Modification of the Food Necessary for Dogs and Cats Undergoing Weight Loss?

The simple reduction of quantity of an adult maintenance diet for weight loss is considered contraindicated and can lead to a 'starvation' situation with deficiencies of protein, essential amino acids, essential fatty acids, minerals, vitamins and trace elements. Lean body mass retention is important for maintaining resting energy requirement. While some degree of lean body tissue loss is an obligatory physiologic response to weight reduction, the objective of a healthy weight loss program is to promote fat loss and minimize loss of lean body mass. Three diets differing in protein level (20%, 30% and 39% of energy intake) were fed to 42 obese dogs. The diet with the highest protein content led to an increased loss of fat mass and minimized lean tissue losses.15 Cats with similar energy intakes of 170 and 177 kcal/day of a diet providing 39.1% and 8.9% energy from protein and fat, respectively, lost more body fat and less lean tissue than cats consuming control diet (30% energy from protein and 9% energy from fat).16 Results of these studies indicate that diets for weight loss in dogs and cats should provide >30% energy from protein. The diets for weight loss should be reduced in energy to maintain adequate dry matter intake and replete in essential nutrients to prevent malnutrition.

Is it More Difficult to Induce and Maintain Weight Loss in Obese Females Compared to Obese Males?

It appears that more severe energy restriction might be necessary to induce weight loss in female dogs. The energy restriction to maintain a 1-2% weekly weight loss rate in 8 beagle dogs housed in kennels had to be more severe in females (54% of MER for target BW) than in males (74% of MER for target BW).9 At comparable body weight, obese female beagles had to consume 12% less energy than obese male beagles to induce weight loss. Further energy restriction of 20% was required in females to maintain the same weight loss rates of both genders. Those levels of energy restriction led to a weekly rate of weight loss of 1.40 and 1.21 % of BW for the male and female group, respectively. Target BW and optimal body condition were reached within 21 to 28 weeks for males and 21 to 32 weeks for females. Therefore, it is possible that to induce the same weight loss rates in both sexes, weight loss protocols for females should be more energy restricted.

Is Feeding an Uncontrolled Amount of a Low-Calorie Food Going to Maintain Body Weight After Weight Loss?

Feeding a low-calorie diet without controlling the amount of diet consumed will not ensure body weight maintenance. Dogs that completed a weight loss program and were continued to be fed a low-calorie diet ad libitum exhibited rebound weight gain that was greatest during the first week of the maintenance period.13 Weight loss at a rate of 1.5% of BW per week or greater was associated with the greatest rate of weight re-gain.

Does Fiber and/or Protein Intake Increase(s) Satiety During Weight Loss in Dogs and Cats?

Begging behavior and scavenging activity driven by hunger are often responsible for failure of weight loss protocols in dogs and cats. Feeling of hunger is reduced and better satiety is induced by ingestion of insoluble, soluble, mixed fiber or higher protein intake in obese humans undergoing weight loss.17-20 There is a marked discrepancy in canine studies, with some suggesting a satiety effect of fiber21,22, while others failing to detect a significant reduction in appetite.23 Weber et al demonstrated that a diet formulated to contain high contents of both protein (10.3 g/100 kcal) and crude fiber (6 g/100 kcal) had a greater satiating effect than did diets formulated to contain higher contents of either protein (10.4 g/100 kcal) or fiber (8.7 g/100 kcal) alone.24 Furthermore, the high-fiber diet had a superior effect on satiety than the high-protein diet, and the high-protein, high-fiber diet had a satiating effect even when fed at an energy-restricted level. This study indicates that weight loss diets designed to provide increased level of protein and fiber may have the most favorable satiety effect.

Which Pharmacological Obesity Treatment Works?

Dehydroepiandrosterone (DHEA), 17-ketosteroid of adrenal and gonadal origin, has been used with a low-fat/high-fiber diet to facilitate weight loss in obese dogs in a clinical trial. However, despite the potential therapeutic value, its utilization in dogs can not be recommended at this time, due to uncertain effects.25

Injections of human recombinant leptin were studied in dogs.26 With a daily subcutaneous dose of leptin, obese beagles lost approximately 16% of body weight in 4 weeks. However, after the end of the experiment, dogs gradually returned to their initial BW. This treatment can not be recommended at this time due to the lack of long-term studies.

Treatment protocol with the appetite suppressant dirlotapide (Slentrol®) in client owned obese dogs resulted in weight loss of nearly 14% in 6 months.27 While treatment with dirlotapide resulted in effective weight loss without dietary modification, the removal of the drug resulted in a rapid return of appetite. Therefore, it is critical to promote owner's behavioral change and adjust the dog's diet in order to maintain the new body weight long-term.

Do High-Protein, low-Starch Diets Perform Better than Traditional High-Protein, Moderate-Starch Diets in Weight Loss Trials in Dogs and Cats?

High-protein low-carbohydrate (sugars, starches) diets as a means of promoting weight reduction have been receiving attention in humans. The premise of an Atkins' type diet in humans is that weight loss is promoted by the metabolism of body fat without caloric restriction. It has been speculated whether a similar 'metabolic shift' works in dogs and cats. Commercial pet foods that are relatively high in starch content are often blamed as a contributing factor to weight gain, especially in cats. Despite much speculation about the efficacy of low-carbohydrate diets (<15% of energy from sugars and starches) for weight loss in cats, studies that would provide evidence of their superiority are lacking. Michel et al concluded that the determinant of weight loss in cats fed either low-carbohydrate (sugars, starches, fiber) or high-carbohydrate (sugars, starches, fiber) diet was not the type of diet but body condition and energy intake.28 In this study, the overweight cats lost weight when their energy intake was reduced regardless of the diet type.

High-protein low-starch (starch 5.3% DM) diet was found effective in reducing BW when fed in a restricted amount to dogs.9 Although the weight loss was more rapid in the control group that was fed traditional prescription weight loss diet (starch 23.9% DM), the high-protein low-starch diet tended to better preserve lean muscle mass, however, these differences did not reach significance.

Bierer et al demonstrated that feeding a high-protein low-carbohydrate diet to dogs in the amount restricted to 85% of MER resulted in higher weight loss rates and increased reduction of fat mass than a high-carbohydrate diet that was fed in the same energy allocation.29 These studies demonstrate that change of the macronutrient profile of a canine weight-loss diet from high-carbohydrate to low-carbohydrate can promote weight loss while preserving lean muscle mass. However, it should not be forgotten that not only macronutrient profile change but also decreased caloric intakes were necessary to achieve effective weight loss.

Can Fatty Acid Modification Promote Weight Loss in Dogs and Cats?

Conjugated linoleic acid (CLA) was studied as an aid for increasing weight loss and preserving lean muscle mass in many animal species and humans.30,31 CLAs are synthesized by ruminants and are naturally found in dairy and beef products. An in vitro fermentation trial showed that CLAs are produce in very low quantities by the intestinal bacteria in dogs.32 In dogs, the addition of CLA (0.6% DM) to a low-calorie high-protein diet (55% DM) had no benefit on weight loss and body composition.29

The antiobesity effect of diacylglycerol (DAG) has been studied in mice, rats and humans. When DAG replaced a part of dietary fat, weight reduction was observed.33 Umeda et al revealed that DAG-containing food, although similar in the caloric content to the triacylglycerol (TAG) containing food, fed to a group of obese dogs, resulted in a significant reduction of BW of 2.3% within 6 weeks, while TAG-fed dogs maintained their obese body weight.34

More studies are needed to investigate the antiobesity potential of CLA and DAG in dogs and cats.


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Iveta Becvarova, DVM, MS, DACVN
Blacksburg, VA

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