Grup de Recerca en Nutrició, Maneig i Benestar Animal, Facultat de Veterinària, Universitat Autònoma de Barcelona
The World Health Organization defines obesity as 'abnormal or excessive fat accumulation that presents a risk to health'. Prevalence of overweight and obesity in a variety of countries has been reported to range between 17 and 41%1-6 for dogs and between 19 and 52%7-13 for cats.
Body condition score (BCS) is the main tool to diagnose overweight and obese cats and dogs. The 9-point scale system has been validated with other more objective measurements of body fat in dogs14 and cats15. In this system, each BCS above 5 (ideal) indicates an excess of 10-15% of body weight. A BCS of 6-7 indicates and overweight animal and BCS of 8-9 indicate obesity.
The most important risk factor associated with obesity in pets is sterilization. A recent publication shows a decrease in physical activity in spayed cats as well as increased energy intake.16 Other risk factors include age, breed, free feeding regimes, endocrinopathies, physical inactivity, and indoor living.17,18
In dogs, obesity has been associated to health problems such as insulin resistance19, pancreatitis 20, hyperlipidemia21, exacerbation of orthopedic disease and shortened life span22, and skin disease1. In cats, diseases associated with obesity include diabetes mellitus, dyslipemias23, hepatic lipidosis, dermatological disease, and lameness.8,24
The mainstay treatment of obesity consists on decreasing energy intake to cause a negative energy balance and mobilization of fat stores. Although this concept is simple, success is often difficult, since a decrease in energy expenditure when faced with energy restriction (thus opposing weight loss) has been described in a variety of species, including cats.25
How Much to Feed?
A thorough diet history (including main diet, treats, table scraps, etc) will allow us to determine the amount of energy needed to maintain a stable body weight. Once this amount of energy is known, feeding 80% of this value can be used as a starting point for the weight loss plan.
If the current energy intake cannot be calculated (such as in free feeding regimes or presence of unmonitored food sources), energy requirements of cats and dogs can be calculated using formulas. There are a wide variety of formulas used for this purpose, and it is important to realize that they can grossly over and underestimate the energy needs of individual patients. For dogs, this author uses the following formula (in kcal per day): body weight (kg)0.75 x 70. For cats, the formula used is body weight (kg)0.75 x 56. This author uses current body weight for the calculations, since ideal body weight can be difficult to estimate.
What to Feed?
Commercial diets specifically formulated for active weight loss are the best choice for obesity management. There are a few studies showing their efficacy for safe weight loss.26-28 These diets are lower in energy density than maintenance diets. This can be achieved using fiber, water, or air. There is some evidence in dogs that fiber contributes to satiety, although this is still controversial.29-31 More importantly, these diets are boosted in protein, vitamins, and minerals in order to avoid deficiencies while restricting energy intake. For this reason, maintenance diets are usually not adequate for active weight loss. High protein diets (>30% on a metabolizable energy basis or >9 g protein per 100 kcal) are recommended, since there is some evidence that they might help maintain lean body mass32 and improve success in dogs.33
Treats should be part of a weight loss plan, to increase compliance. No more than 10% of the total daily energy should come from treats to avoid unbalancing the diet by nutrient dilution (by providing calories but not the other required nutrients in the adequate proportions). Fruits and vegetables are low in energy density and are excellent treats, especially for the canine patient.
Monitoring
Monitoring is the most important part of the weight loss process. After starting energy restriction, this author recommends re-weighing the patient after 2 weeks. Three things can happen: the patient lost weight, gained weight, or stayed the same weight. The last 2 scenarios are more likely if a good diet history and estimation of original energy intake was not obtained. It is generally accepted that a rate of 1-2% body weight per week is ideal. Faster rates can be associated to lean body mass loss.34 Also, feelings of hunger and unacceptable behavior are more likely to happen.
If the patient gained weight or had not changed weight, further restriction (10-20% more) is indicated. If the patient is losing weight too fast, energy intake should be increased by 5-10%. If the weight loss rate is too slow, energy intake should be restricted 5-10% more. In all cases, a reweigh after 2 weeks is important to make sure the weight loss plan is working. If the patient is losing weight at an adequate rate, weigh-ins are recommended every 3-4 weeks. A plateau can be reached later in the process, so monthly revisions of the weekly weight loss rate and owner compliance are extremely important. Owners need to be prepared for the long haul, and should receive frequent encouragement along the way.
Prevention
The best time to address prevention of obesity is at puppy or kitten wellness visits and at the moment of sterilization, especially in animals at risk for obesity. Recommendations to decrease food intake by 30% should be made to owners after the procedure, since a decrease in food intake as high as 30% has been reported to be necessary to maintain body weight after spaying/neutering cats16 and dogs35. Meal feeding should be recommended since free feeding regimes have been associated with obesity. Providing owners with a BCS chart and with a standard measuring cup is recommended.
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