Maintaining lean body mass can impact longevity. Optimal body condition, together with sustained lean body mass, is important for overall health.1-3
Lean body mass (LBM) includes skeletal muscle and organs, essentially everything except fat. It serves as an amino acid reservoir from which dogs and cats can build the proteins that are essential components of every cell, including immune cells, red blood cells and hormones.
With age, protein degradation often exceeds synthesis and this imbalance leads to progressive loss of LBM. This age-related loss of LBM, unrelated to disease, is called sarcopenia.
Sarcopenia in dogs and cats (and people) is associated with increased risk for mortality and other health problems.4
Keeping LBM loss to a minimum can help cats and dogs better maintain health, and potentially live longer.
Insufficient dietary protein may contribute to loss of LBM. Further, inadequate protein intake and loss of LBM can compromise a pet’s immune system, leaving them at greater risk from infections and other stresses.5
Historically, adequate protein requirements for dogs and cats have been calculated based on the amount of protein needed to maintain nitrogen balance. Yet multiple studies show that higher amounts of dietary protein are needed to maintain LBM.6-9
While cats need only 1.5 grams of protein per kilogram body weight to maintain nitrogen balance (protein) they need over 5g protein/kg body weight to maintain LBM.6
Dogs also require about three times more protein to maintain protein/DNA ratios (an indicator of protein reserves) compared to that needed to maintain nitrogen balance, and old dogs need 50% more protein than young dogs regardless of the measure used.8
Purina studies have shown that a higher lean body mass in cats is associated with longevity, while the loss of lean body mass in dogs is linked with shorter survival times. Research shows that higher protein diets can help preserve both LBM and body weight in cats and dogs.
At all stages of life, maintaining ideal body weight is key to maintaining LBM. However, Purina studies show that cats commonly lose body weight and LBM after about 12 years of age. In some aging cats, this loss of weight and LBM leads to what may be referred to as the “skinny old cat syndrome.” Although nutrition cannot completely prevent sarcopenia in aging cats (or dogs), nutrition can play a role in delaying some of the age-related changes in body weight and body composition of these older felines.1
A cross-sectional study of 256 cats showed they begin to lose both LBM and fat at approximately 12 years of age.1,9
This progressive loss of LBM, called sarcopenia, poses a risk for health problems and a shorter life span.
A longitudinal study of aging, non-obese cats, showed that every 10-gram increase in LBM resulted in a 2% increased chance of survival.1,10
Purina research also demonstrated that older dogs fed a high-protein diet showed slower age-related loss of LBM than dogs fed a diet lower in protein.11
High-protein, low-calorie diets significantly increased fat loss and reduced loss of LBM in overweight cats undergoing weight loss when compared with cats fed normal protein, low-calorie diets.12
Purina research with overweight dogs showed that a high protein diet helps protect LBM during weight loss.13
In this study, overweight dogs fed a diet with a higher percentage of calories from protein lost more fat and retained more LBM while moving closer to their optimal body condition.
Loss of LBM during weight loss is common, but undesirable. Since lean body mass burns more calories than fat tissue, preserving LBM may help to prevent future weight gain.
Body composition and LBM are much better indicators of overall health in dogs and cats than body weight.13,14
A body condition score assessment is a focused, hands-on examination that veterinarians can use to evaluate the body composition of dogs and cats. Owners can also be taught the same method to monitor their pets.
Purina scientists developed and validated the 9-point Body Condition Score system (BCS) for cats and dogs, which is a simple method for estimating body fat and determining a pet’s optimal body condition, regardless of breed or body weight.14,15
Independently validated and published in peer-reviewed journals,16-18 this practical tool to support nutritional management for dogs and cats is now used by veterinarians worldwide.
In addition to assessing body condition, which primarily evaluates body fat, a separate evaluation of muscle mass is also important. The 4-point muscle condition scoring system (normal, mild, moderate, or severe loss of muscle mass) can help account for losses of LBM that may occur even in overweight pets.19-21