Too much of a good thing

In developed countries where commercial food provides the majority of a dog's or cat's calories, overweightedness and obesity may affect as much as 40% of the pet population. No other health concern presents as many challenges and opportunities to the petfood industry.

It's vital to prevent gradual weight gainsmall changes can have a big impact over time.
It's vital to prevent gradual weight gainsmall changes can have a big impact over time.

In developed countries where commercial food provides the majority of a dog's or cat's calories, overweightedness and obesity may affect as much as 40% of the pet population. No other health concern presents as many challenges and opportunities to the petfood industry.

Consider how prevalent obesity has become in the human population. How does that translate to our pets? A study examining nearly 15,000 US canine patient records from 1999 to 2004 showed 21.6% of the dogs were overweight and 14.8% were obese-a total of 36.4% (Weeth et al., 2007). In France, 385 cats were studied, revealing 19% as overweight and 7.8% obese-a total of 26.8% (Colliard et al., 2009).

Part of the challenge in fighting this problem is that many pet owners have difficulty recognizing when their animals are overweight. This means we need to provide some tools.

Body conditioning was developed by Nestle Purina PetCare for companion animals and has been validated in scientific studies correlating to fat mass and body mass. On this scale ( Figure 1 ), an animal with an ideal body weight has a visible abdominal tuck and waistline, and if you were petting the animal, you'd be able to readily feel its ribs.

To make consumers aware of appropriate body conditions, the industry has an opportunity to do some education, and the most prominent place is on packaging-not just showing the chart but also providing descriptions and feeding recommendations based on body conditioning.

Feeding guidelines are not foolproof because energy requirements vary tremendously among pets. Our industry is very good about providing species-specific values for different weight ranges and lifestages, but these usually don't have volume ranges. Generally people will think their animals are hungry and feed more, not aware they're feeding an excess of calories.

We have to consider volumetrics, in which people associate the amount of calories with volume rather than by the actual foodstuff. Consider two dry petfoods, 1 cup each, with the first food having 220 kcal and the second, 634 kcal. That's almost a threefold difference. If a consumer simply feeds the same volume regardless of the food's energy density, there's increased potential to overfeed.

We can help pet owners with portion control by providing such calorie information. In North America, this is usually by cup (volume); you could also provide it by unit of mass (kilograms) and may want to include both if your products are sold globally.

The Association of American Feed Control Officials (AAFCO) has been weighing a proposal for several years to require calorie information on petfood labels in the US. Most industry trade groups oppose it. The American College of Veterinary Nutrition supports it, as does the American Veterinary Medical Association representing 50,000 veterinarians. If vets try to use current intake of food as a basis for where an animal's real energy requirements lie, it becomes very challenging without calorie information.

Besides providing these tools, petfood manufacturers can follow one or more nutritional strategies.

Lower energy density

The premium and superpremium petfoods that have become so popular generally have higher energy density and fat. To lower density, you can use a variety of mechanisms, though each presents challenges:

  • Higher fiber provides volume and mass without providing calories. Large amounts of soluble fibers are usually avoided due to the concern of loose stools. Consumers may perceive fibers on the ingredient declaration as filler, even though they are potentially costly. There's a great deal of debate about fibers' satiety effect.
  • Lower fat decreases the energy density because fat delivers more energy per gram. Higher fat foods are generally more palatable, so lower fat may affect palatability.
  • Higher moisture provides volume and mass while decreasing energy density. With wet petfoods, you can increase water from 75% to 85%, which can be very effective, especially for a single feeding because such a large volume fills the gut. Multiple feedings throughout the day would negate some of the effects, and there are questions about satiety.
  • Expansion of dry kibble provides increased volume without affecting mass. More expanded kibble has air pockets and feels lighter. There's debate over whether this affects palatability, but probably not. The satiety effect is unknown. This may be more of a helpful tool for pet owners in terms of portion control, because they don't perceive they're feeding less.

Note that AAFCO regulations determine whether you can label or market products as "lite," "reduced calories" or "lower fat" as well as how a product with moisture over 78% is labeled.


While not an amino acid, this ingredient is involved in fat metabolism, and its benefits in reducing energy and calories are well supported by research (Roudebush et al., 2008).

Other nutrients backed by published literature (though with varying levels of support) include conjugated linoleic acid, which comes mainly from dairy or meat ingredients and has potential to keep animals leaner; vitamin A at higher levels than normally used; and diaglycerol. These ingredients fall into the generally recognized as safe (GRAS) category, meaning they're usually accepted for use in petfoods.

Nutrient enhancement. The concept is to add each essential nutrient above required minimum value, which allows you to restrict calories without creating nutritional deficiencies. The level of caloric restriction is proportional to the enhancement:

  • x = 100/(%/100), where x = level of restriction supported;
  • Thus, 125% enhancement supports 80% restriction (100/(125/100)=80).

Caloric restriction without enhancement can result in nutrient deficiencies. Petfoods formulated according to this concept have evolved from veterinary/therapeutic lines to over-the-counter products.

Lower carb/higher protein

Though not an official definition, "low carb" typically means less than 20% by difference as fed for dry foods. (Carbohydrate claims are currently under review by AAFCO.) These types of dry foods can be very technologically challenging to produce because you're reducing the ingredients that bind others together. Challenges with energy density might also arise because the products have higher fat content.

Many of the lower carb petfoods are also "grain free," using ingredients like potatoes, peas or tapioca as the main source of starch. Occasional concerns are raised regarding the higher protein and mineral content of these foods, but research has shown the approach to be safe (Liu et al., 2009; Vester at al., 2009).

Powerful proof

Many of us in the petfood industry are focused on making products that try to improve lifespan as well as quality of life. The only thing that's been definitively shown to do that from a nutritional as well as medical perspective is caloric restriction.

A very impressive study, conducted over 14 years, looked at Labrador Retriever littermates randomly separated into two groups that received the same living conditions, care, exercise level and food (Lawler et al., 2008). With the experimental group, the amount of calories they consumed was restricted by 25% to ensure the dogs remained lean compared with the control group, which was allowed to become about 10 to 20% overweight.

The dogs that were kept lean lived almost two years longer than the control group. Equally profound is that clinical signs of some of the chronic diseases that we see in older pets, such as osteoarthritis, were much delayed.

This has not been studied in cats, but it's been true in all species studied so far, including monkeys, worms and rats.

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