Obesity is a growing problem in cats worldwide, but, in Western societies, the incidence of excess weight and obesity in cats
is reaching truly worrisome numbers. Studies have indicated that 15% to 35% of cats in the United States are overweight or
obese, and practitioners estimate even higher percentages in some areas.1 Obesity is defined as having a body weight 20% or more above the ideal weight. In other words, a 4-kg (9-lb) cat that gains
1 kg (2 lb) is considered obese. Using this definition, it would not be surprising for feline obesity to approach 70% in some
practices. Furthermore, obesity is not just a cosmetic problem. In cats, it increases the risk of diabetes and hepatic lipidosis
and is associated with increased incidences of many other conditions, such as lower urinary tract disease and osteoarthritis.2 This serious medical condition not only increases morbidity but can also shorten life span. Considering the number of affected
cats and the challenge of getting a seriously obese, 12-kg (26-lb) cat to weigh 4.5 kg (10 lb), it is obvious that the situation
demands our full attention.
To successfully address feline obesity, practitioners must recognize obesity as more than just overeating but as an endocrinopathy,
and they must be able to develop safe and effective weight loss programs and help every member of the veterinary team understand
how important it is to prevent young cats from gaining excess weight in the first place.
Obesity as a multifactorial, multisystemic disease
The most obvious reason for any animal becoming obese is that it is consuming more energy than it is expending. In cats, this
energy imbalance can occur when there is an excessive intake of calories (food or treats) or a reduction in energy expenditure
(reduced activity because of an indoor lifestyle, illness, or injury). However, there are many other factors that play significant
roles in the development of obesity. These factors include genetic predisposition, sex, neuter status, hormonal disturbances,
and other conditions that can influence or control appetite, metabolism, or homeostasis. As a result, it is important to:
- Make a concentrated effort to recognize risk factors, including early recognition of feeding behaviors or lifestyle situations
that are leading to weight gain.
- Carefully monitor young and middle-aged cats to identify and correct weight gain early.
- Promote obesity prevention and the health benefits of weight control from kittenhood on.
- Be actively involved in body assessment (weight measurement and body condition scoring) of all cats at every veterinary visit.
In other words: Act before the cat is obese! Obesity prevention must start early, and the veterinary team is essential to recognition, early intervention,
and successful lifestyle changes.
For both male and female cats, neutering is an important risk factor for obesity.3,4 Many cats gain significant weight after neutering or during adolescence, and it had been believed that this gain was due
entirely to the type or amount of food fed and not due to other factors. However, several recent studies have shown that multiple
hormonal changes occur immediately after removal of the sex organs, and these changes have a significant effect on appetite,
metabolism, and other hormones determining metabolic status.3,5-7 The metabolic changes include alterations in levels of leptin, progestins, estrogen, prolactin, insulin-like growth factor
(IGF-1), and other hormones.3,5-7 The results are an increase in appetite, a reduction in energy metabolism, changes in glucose tolerance and lipid metabolism,
and in the case of IGF-1, an increase in the number and size of adipocytes.
Spayed and neutered cats undergo a startling series of hormonal changes that affect food intake (they have an increased appetite)
and energy metabolism (their energy needs are decreased) that results in an increase in body fat mass that may be inevitable
unless appropriate measures are taken to monitor and limit intake — particularly in indoor or sedentary cats. To prevent obesity
in these cats, careful control of intake (no free-choice feeding) immediately after neutering (a reduction in intake of at
least 25% to 30% is essential) and close monitoring of body weight and body condition score (BCS) are necessary to make the
appropriate adjustment. Several studies have evaluated the role of different amounts of dietary components (e.g. fat or carbohydrates) in relation to obesity, but the key factors that result in increased body weight are gonadectomy and