Is fatty food to blame for the pet obesity epidemic?

Dogs generally receive dry food once or twice each day. Cats are more likely to be free fed with a greater portion of their diet from wet food. It is no secret that ingesting more dietary calories than the body’s expenditure is fattening, but does diet composition matter?

Industrially prepared dog and cat food comes in different forms, ingredient and macronutrient compositions, and caloric densities. Fat provides more than twice as many calories per gramme as carbohydrates or protein. The dry matter of food higher in fat normally is higher in calories. Both commercial dog and cat foods have between 20% and 75% of total calories from fat.

Fat promotes obesity development

Experimental obesity in dogs is typically induced by free-choice feeding of a high-fat food. When compared with carbohydrates, fat promotes obesity development. In a study with adult dogs, unrestricted access to a diet with 51% instead of 23% energy from fat produced a greater increase in caloric intake, body weight and body fat. The high- and low-fat foods were formulated by isocaloric exchange of tallow and corn starch.

Dietary fat is converted more efficiently into body fat

In 2 studies, cats were fed ad libitum on dry foods varying in fat content. Extra lipid was added at the expense of isoenergetic amounts of carbohydrates. Dietary fat levels higher than about 20% of energy generally increased caloric intake, body weight and fat mass.

Offering non-downsized or liberal amounts of higher-fat foods, contrary to lower-fat alternatives, further raises caloric intake in dogs and cats. In energetic terms, dietary fat is converted more efficiently into body fat than carbohydrates.

It is easy to see that pets fed a high-fat diet become overweight if the amount of food is not controlled. Observational data are required to substantiate or refute the expected impact of fatty food during long-term use in the home setting.