Page 485 - Small Animal Clinical Nutrition 5th Edition

Chapter
27

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Obesity

Philip W. Toll
Ryan M. Yamka
William D. Schoenherr

Michael S. Hand

“If we could give every individual the right amount of nourishment
and exercise, not too little and not too much,
we would have found the safest way to health.”
Hippocrates

mated optimal weight. People are defined as mildly obese when
CLINICAL IMPORTANCE actual body weight exceeds optimal body weight by 15 to 30%
(NIH, 1985, 1998; Owen, 1988). Similar definitions have been
Obesity is a real disease and is thought to be the most prevalent proposed for dogs and cats (Joshua, 1970; Lewis et al, 1987).
form of malnutrition in pets of westernized societies. Large Arbitrary ranges for RBWs for overweight dogs and cats are
studies in Great Britain and the United States indicate that the between 10 and 20% above optimal weight. Obese dogs and
prevalence of overweight and obese dogs is between 24 to 30% cats are characterized by RBWs above 20%.
(Lund et al, 2006; Armstrong and Lund, 1996; Mason, 1970; Fat mass, expressed as a percentage of body weight, can also
Meyer et al, 1978; Edney and Smith, 1986). Similar studies be used to define obesity. People are considered obese when
indicate the prevalence of overweight and obesity in cats is percent body fat (%BF) exceeds 20 to 30% of total weight
between 25 to 35% (Lund et al, 2005; Armstrong and Lund, (NIH, 1985; Owen, 1988). Body composition studies of dogs
1996; Scarlett et al, 1994). Being overweight appears to be and cats indicate that animals judged to be in ideal body con-
more problematic in middle-aged dogs and cats; 42% of dogs dition have 15 to 20% body fat (Stanton et al, 1992; Laflamme
and 44% of cats between the ages of five and 11 years are over- et al, 1994, 1995; Burkholder, 1994; Laflamme, 1997, 1997a).
weight in the United States (Lund et al, 2005, 2006).
Deciding when a given animal is in ideal, overweight or Health Risks of Obesity
obese body condition has clinical relevance because overweight Excessive deposition of body fat has detrimental effects on
and obesity may adversely affect an animal’s health. By defini- health and longevity. In people, these detrimental effects begin,
tion, obesity is the accumulation of excess body fat. Body and thus obesity has been defined, when body fat exceeds 20 to
weight increases as fat accumulates; thus, having excessive body 30% of body weight (NIH, 1985; Lew and Garfinkel, 1979).
fat and being overweight are related. Although body weight can Even being moderately overweight throughout life reduces
increase for multiple reasons (Burkholder and Toll, 2000), the lifespan. In a lifelong study of two groups of Labrador retriev-
majority of overweight dogs and cats have excess body fat. er dogs, the treatment group was fed 25% less than the control
Body weight relative to an animal’s optimal (ideal) weight group (Kealy et al, 2002). Over the course of the study, the con-
has been used as a defining criterion for obesity because body trol group became moderately overweight.The median lifespan
weight is easier to measure than body fat. Relative body weight of the leaner group was 13.0 years compared to 11.2 years for
(RBW) is simply an animal’s current weight divided by its esti- the moderately overweight dogs. Many pet dogs and cats are