Overall approach

After the initial assessment is complete, formulate an individualized weight loss plan. The plan should include the determination of the following:

1. Ideal BW
2. Caloric restriction
3. Food selection and treat allowance(s)
4. Feeding management and activity plans
5. Scheduled follow-up

Determine daily caloric intake

The approach to determining the daily caloric goal for weight loss depends on the presentation and history of the patient.³⁹ Any method of caloric restriction is merely a starting point and subject to individual metabolism. Regular monitoring is essential to ensure healthy weight loss and allow for necessary adjustments in caloric intake. Two options for determining the daily caloric requirements for weight loss are the following:

1. Feed an amount to provide 80% of the current caloric intake. That approach may be effective in patients that are overweight and are at a stable weight with an accurate diet history. However, if a pet is actively gaining weight, a greater reduction may be required to promote effective weight loss.
2. Calculate the resting energy requirement (RER) using the pet’s estimated ideal weight then feed a percentage of that amount. Although there is no established standard reduction, feeding 80% of ideal-weight RER is effective and well tolerated.^40,41 Calculate the daily RER for ideal BW in kg using one of the following two equations. Note that the first equation can be used for patients of any weight. The second equation is used for patients weighing 2–25 kg, but note that the second equation is not as accurate as the first equation as it will overestimate the caloric needs of patients weighing either < 2 kg or > 25 kg.

RER in kcal/day = 70 x (ideal BW[kg])0.75

RER in kcal/day = 30 x (ideal BW[kg]) + 70

Select a diet

Select a diet based on the caloric restriction desired, the degree of obesity, and the preferences of the patient and client. Inquire about preferences regarding flavor and dry versus canned foods. Evaluate and prepare a list of diet options that vary within those parameters if the first or second choice does not meet with acceptance from the client or pet. Determine availability and affordability concerns that might influence diet selection.

Before starting a plan, make sure that everyone involved in the pet’s care is interested and receptive, ensuring that the plan is practical and feasible for the client’s abilities and lifestyle. Then calculate the daily food dose and translate that dose into quantities of cans and/or cups/day. If possible, weigh dry food on a scale because measuring with a cup may be imprecise, particularly with the small amounts needed for cats and small dogs (calculate the food dose using the kcal/kg obtained from either the pet food label or the manufacturer).⁴² Incorporate a treat allowance of up to 10% of total calories into the daily caloric goal. Explore, address, and realign client expectations if necessary.

Essential nutrients in pet foods are balanced according to caloric content, so when portion size (and thus calories) is reduced, so are the amounts of essential nutrients. A review of the process for a comprehensive analysis of nutritional adequacy of a diet is beyond the scope of these guidelines; however, evaluating a diet for sufficient protein is an important step for weight loss plans.

Consider dietary protein on an energy basis (in g/1,000 kcal) to evaluate the impact of the proposed reduction of caloric intake on National Research Council recommended allowances (Table 2) For a quick rule of thumb to ensure that the diet contains adequate protein, select foods that provide cats with ≥ 5 g/kg BW and dogs with ≥ 2.5 g/kg BW based on ideal BW (See Evaluating Protein Sufficiency sidebar.).^43–45

A therapeutic food is defined as a pet food that was purpose formulated to help modulate either a disease or condition. Therapeutic foods are only available either through a veterinary office or with a prescription from a veterinarian. Using a therapeutic weight-loss diet is preferred over using reduced amounts of over-the-counter (OTC) diets because therapeutic diets are more likely to provide adequate nutrient intake when fed in calorically restricted amounts.

Therapeutic weight loss diets are formulated to contain more protein, vitamins, and minerals/calorie than OTC foods, ensuring adequate nutrient intake during caloric restriction. High protein may preserve muscle mass during weight loss and may improve satiety.^46,47 As the effects of aging on protein digestibility are not well understood, senior pets may require closer monitoring of protein intake (and MCS) during weight loss.⁴⁸ Therapeutic foods also may be lower in fat, higher in fiber, and/or higher in moisture to decrease caloric density. That allows clients to feed a greater volume of food with fewer calories.

The role of fiber in satiety for dogs and cats is controversial and likely varies among pets.^46,49–51 The crude fiber analysis, which is required on a pet food label, accounts for only the insoluble fiber fraction and none of the soluble fiber content and is an underestimate of the true fiber content of most pet foods. Diets containing insoluble fiber purportedly have a lower caloric content by volume and may promote satiety, leading to better diet plan adherence.⁴⁶ Insoluble fiber may cause an increase in the volume and frequency of bowel movements.⁵² Discuss that potential effect of fiber with clients when selecting a diet.

Restricting the amount of OTC maintenance food that is fed, especially diets with high caloric density, generally fails to provide satiety for most pets, contributing to poor adherence and client frustration. Restricting amounts of an OTC maintenance diet fed could also lead to deficiency of one or more essential nutrients.⁵³

The current median kcal/cup of therapeutic and OTC dry foods marketed for weight management are 301 kcal/cup (dogs) and 342 kcal/cup (cats).⁵⁴ However, there is wide variation and there are no nutritional or caloric criteria mandated for the terms such as “less active,” “indoor,” “weight control,” “optimal weight,” or “healthy weight.” Products labeled “less” or “reduced” calories or fat have no restriction on calorie or fat content other than being some amount lower than the company’s chosen comparison product. Foods with labels stating “lite” or “light” must contain less than a certain amount of calories/kg set by the American Association of Feed Control Officials (AAFCO), although there is no restriction on calories/cup or can.²² For specific definitions and amounts that qualify as “light,” see the AAFCO 2013 Official Publication.²² Due to the wide variability of products with such labeling, achievement of weight loss requires careful evaluation of those products on a case-by-case basis.

When advising clients about amounts to feed, it is best to do so based on a caloric target, not just a variation on the label range. Pet foods that show similar caloric content/cup or content/can may show entirely different recommendations about the amount to feed. Compare the caloric density, not the label feeding amounts, to determine caloric intake.

In some instances it may be appropriate to adjust volume alone and not change to a therapeutic diet if the pet can lose weight with modest caloric restriction and without feeding below the label guidelines to provide calories for ideal weight. That process will ensure the pet receives adequate nutrients. For example, that approach may apply to either cats being transitioned to meals from free feeding or to pets just slightly overweight and easily able to increase activity.

There is little to no evidence showing that any nutritional supplement aids in weight loss.⁵⁵ There is one FDA-approved pharmaceutical a that is currently available for the management of obesity in dogs. That medication was evaluated in a safety and efficacy study up to 1 yr’s duration when used with a maintenance diet.⁵⁶ As with any medication, it may not be appropriate for every patient.

TABLE 2

Minimum protein requirements in diets⁷²

BW, body weight; NRC, National Research Council; RER, resting energy requirement.

Evaluating protein sufficiency using RERs and BW ^67,68

Because labels do not show protein content in g per 1,000 kcal, the g of protein being fed can be calculated using the “guaranteed analysis” and the following information:

Assume an overweight dog with 10 kg ideal body weight. Assume your food label shows 21% crude protein and contains 3,490 kcal/kg.

1. Calculate dog’s caloric needs at 80% resting energy requirements (see text), use the following equation:
   • 80%(70 x 10 kg0.75) = 315 kcal/day
2. Calculate g of protein in the food using the following equation:
   • (% crude protein/kcal/kg) x 10,000 = g/1,000 kcal of food
   • 21/3, 490 kcal/kg x 10,000 = 60 g/1,000 kcal
3. Determine dog’s daily protein requirement using the following equation:
   • ≥ 5 g/kg for cats and ≥ 2.5g/kg for dogs
   • 2.5 g/kg x 10 kg BW = 25 g protein/day
4. Determine dog’s daily protein requirement using the following equation:
   • 315 kcal/day x 60 g/1,000 kcal = 18.9 g/day
   • 18 g < 25 g

This food does not provide sufficient protein.