12 Oct 2015
Cecilia Villaverde
Job Title
Figure 3. Frequent weigh-ins are important to adjust the energy allowance of the patient. Paediatric scales provide good precision for small dogs and cats.
Obesity is a common condition in dogs and cats, ultimately caused by an unbalance between energy intake and expenditure. It has serious consequences for the health and longevity of our pets. The most common diagnostic tool to identify this problem is the body condition score, which should be used for every pet, every visit and taught to owners to perform at home to prevent obesity developing.
Prevention is very important in patients more at risk, such as spayed and neutered dogs and cats. If a pet already has obesity, treatment consists of reversing the energy imbalance by increasing energy expenditure and decreasing intake. The use of therapeutic weight loss diets will help promote satiety and prevent nutrient deficiencies, including protein, reducing the likelihood of rebound.
A diet should be fed in low enough amounts to promote weight loss and adjusted every two to three weeks, since the use of formulas or label instructions is not precise due to the high variability of individual energy requirements. Long-term follow-up and controlled feeding practices are essential to prevent recurrence of this condition.
Excess bodyweight is a common condition, with an estimated prevalence of around 26% to more than 50% in Western countries1-4.
Obesity is defined by the World Health Organization as an excess of body fat with negative effects on health, as well as being a multifactorial disease, with both genetic and environmental causes.
Overweight dogs and cats are those that have a body fat percentage higher than 20% to 30%. Several techniques to measure body fat exist, such as dual energy x-ray absorptiometry (DEXA).
These techniques, although commonly used for research purposes, are too complex and costly to be of use in the clinical setting at this time. For this reason, clinicians use practical methods to estimate excess body fat.
In the nine-point scale, four to five is considered ideal and scores above five are overweight (six to seven) and obese (eight to nine). These BCS systems, despite being subjective and semi-quantitative, have been validated with an objective quantitative measure of body fat (DEXA). This validation shows each BCS point above five equals approximately 10% to 15% excess body fat.
Figures 1 and 2 show a canine and a feline BCS chart, obtained from the nutrition toolkit of the World Small Animal Veterinary Association (www.wsava.org/nutrition-toolkit). Vets should assign a BCS score to each patient at each visit and must teach pet owners to perform it regularly at home, so they know what their pet should look and feel like during its lifetime.
Simply put, obesity results from an excess of energy intake compared to energy expenditure.
Treatment consists of reversing the balance, by increasing energy expenditure (via physical activity) and reducing energy intake (via caloric or energy restriction).
Physical activity has to be low impact and always tailored to the patient to avoid injuries. Additionally, some might have comorbidities that make them exercise-intolerant. Calorie restriction requires developing a feeding or nutritional plan.
Pets can lose weight with any diet, as long as they eat less calories than before. So, why are there therapeutic diets on the market to address this issue? These diets have two characteristics that make them desirable for weight loss plans.
The first is they are lower in energy density than average maintenance diets. The most common strategies used to achieve this are the inclusion of fibre, water or even air and the reduction of dietary fat. Different diets use a different combination of these strategies. Most of these diets are high-fibre, due to its satiation effect10, thus a slow transition is indicated and the owner needs to be aware his or her pet will defaecate more and with increased frequency.
The second trait of therapeutic weight loss diets is the fact they are nutrient-fortified. Maintenance diets are formulated to provide all essential nutrients for adult dogs and cats when they are eating their maintenance energy requirements (MER). During calorie restriction, energy intake has to be dropped – sometimes considerably – below this MER and pets eating a maintenance diet will be getting not only fewer calories, but also fewer nutrients. All nutrient deficiencies are undesirable, but protein deficiency is especially worrisome.
When losing weight, fat mass loss is the desired goal, although there is always some degree of lean body mass loss. Patients losing muscle mass to a high degree have a decreased energy expenditure and are more prone to recurrence (a yo-yo or rebound effect). Feeding diets fortified in protein will attenuate lean body mass loss11. Therapeutic canine weight loss diets usually provide more than 30% of the calories for protein, whereas feline therapeutic weight loss diets usually provide more than 40% protein calories.
The short answer to how much to feed is “less than before” and always portion-controlled. Obese pets fed at will cannot lose weight. Ideally, each pet should get a detailed diet history that allows accurate estimation of current energy intake. In a weight-stable pet, this would be its true MER.
A good starting point for weight loss is to take that true MER and drop it by 20% to 30%.
However, knowing the true MER is not always possible – for example, in households with multiple pets sharing feeding bowls, in pets that have constant access to food or in pets that receive a variety of treats or table scraps.
For these cases, we can use formulas to estimate the MER and drop that value by 20% to 30%. Several formulas and methods are available to do this and the calculations can be done with current bodyweight or ideal bodyweight – the latter being a more aggressive approach.
The error associated with using a formula is around 50%12, thus our initial assessment of the energy needed to lose weight for a particular pet can be way off the mark and we will need frequent monitoring to stay on track. The author uses the resting energy requirement (RER) formula for dogs and 0.8 × RER for cats (RER being 70 × bodyweight [kg]0.75 kcal/day)12.
For owners who want to use treats, this is acceptable as long as they provide only 10% of the daily allowance, leaving 90% for the main diet. The energy content of treats has to be obtained from the manufacturer or from databases (http://fooddatabanks.ifr.ac.uk) if human foods are used. Fruits and vegetables are excellent, low-calorie treats.
Using a therapeutic weight loss diet low in energy density, besides helping with satiation, will give the impression to the owners the energy restriction is less severe than expected. Using bowls commensurate to the amount fed will also help the owners not to overfeed.
Using dry diets with volume measures (cups) can result in high errors13 and owners must use a kitchen gram scale daily rather than rely on cups. Feeding canned food has lower energy density than dry, and it can be easier for owners to portion control – plus, in cats, water has some satiation effect that can help reduce hunger14.
Feeding multiple times a day and other methods of reducing boredom can also help a pet feel less hungry. Hiding food or using food dispenser toys are some ways to achieve this.
Patients should get weigh-ins every two to three weeks to measure bodyweight and BCS (Figure 3). The goal is to lose 1% to 2% bodyweight weekly (1% being more realistic). Losses higher than 2% can result in lean body mass loss and hunger.
If the patient is not in this range, the clinician has to adjust the food amount (Figure 4) after ensuring with the owners all family members are following the plan and the pet has no access to uncontrolled sources of food. This is the most critical part of the process and it is important to encourage the owners and repeat a diet history, to ensure the patient is not receiving additional calories.
Obese patients that have lost weight are at risk for recurrence15 and should be treated as such. Once the pet has achieved ideal BCS, it can stay on the weight loss diet or be transitioned to a maintenance diet (such as a light diet).
After the switch, daily energy intake can be increased in 5% intervals every two weeks until the patient reaches weight stability. After that, the owners should weigh and BCS the pet every month and always feed portion-controlled amounts.
