Although dogs may not be as worried about the social stigma of obesity, being overweight has been associated with many clinical and subclinical conditions that put a pet's health at risk. As we learn more about the associations between excess weight and diseases, being lean is the healthier choice for dogs.
Quality and quantity of life
A lifetime study in Labrador Retrievers found that dogs with an ideal BCS of 4–5/9 lived a median of 1.8 years longer than their slightly overweight counterparts with a median BCS of 6–7/9 (Kealy et al, 2002). These slim dogs also had delayed onset of chronic illnesses. Though some owners worry about restricting their dog's food, a new study has shown decreased quality of life when pets are overweight and improvement of these measures (such as vitality, emotional disturbance and pain) after successful weight loss (German et al, 2012).
Osteoarthritis (OA)
In the study of Labrador Retrievers, it was also shown that leaner dogs also had delayed onset of OA compared with their overweight counterparts (Kealy et al, 2002). Fortunately, lameness and pain in dogs can be alleviated with weight loss; even weight loss of 6-8% of total bodyweight has shown significant decreases in subjective and objective lameness scores (Marshall et al, 2010).
IVDD
A study of 700 dogs showed obese dogs of all breeds were at increased risk of IVDD, but in high risk breeds (particularly the Miniature Dachshund), even being moderately overweight increased the risk (Packer et al, 2013). For those dogs that must undergo surgery, another study supports the notion that dogs were 7.62 times more likely to have recovered (ambulating without assistance) at the initial 3 to 4 week follow up if they had a BCS of 6/9 or less (Williams et al, 2012).
Subclinical conditions
Fat tissue produces hormones and inflammatory mediators (e.g. adipokines such as leptin) that can predispose pets to diseases or exacerbate current diseases through a pro-inflammatory process (Kil et al, 2010). Obesity has also been related to hypercholesterolaemia, hypertriglyceridaemia, hyperinsulinaemia, increased leptin and decreased ghrelin in dogs (Jeusette et al, 2005).
Cardiorespiratory
Obesity in dogs has been associated with various cardiac and respiratory conditions. Mild cardiac changes were noted in experimental studies of weight gain in dogs (Pelosi et al, 2013), and resting and recovery heart rate was also shown to be affected by BCS and exercise (Kuruvilla et al, 2003). Most notably, obesity is linked to concerning respiratory conditions such as airway dysfunction (Bach et al, 2007) and tracheal collapse (White et al, 1994). Obesity was also found to be a risk factor for death in patients with heatstroke (Bruchim et al, 2006).
Closing thoughts
There are many other clinical and subclinical conditions associated with obesity involving almost every body system. Excess weight is easier to prevent than treat, so alerting owners to these consequences before they are apparent will help keep patients healthier and happier.