Strong, Not Fat: How to Feed for a Healthier Body Shape

Statistics show overweight cats and dogs are at high risk of diabetes, chronic arthritis and even skin disease, and existing cardiovascular or respiratory conditions worsen. Keeping a healthy shape works just like it does for us: build muscle, lose fat.

Chubby pets are adorable — but did you know excess weight may shorten your pet's life? Overweight cats and dogs are high-risk for diabetes, chronic arthritis and skin disease, and heart or airway disease gets worse. Obese animals also carry higher anaesthetic risk.

Muscle raises metabolism and burns fat, and it stabilises and supports the joints, making running and jumping easier.

How to eat for more muscle? Animal protein

Protein is the key to building muscle: it's the raw material, and its quality decides how efficiently muscle grows. When choosing kibble, AAFCO is often the first yardstick — but is meeting AAFCO enough?

Chemical analysis ratios can't directly represent a food's quality. AAFCO's 26% protein standard, for instance, can be met with "fresh chicken" or with "soybeans, chickpeas, peas and lentils".

But the gut can make limited use of those legume and plant proteins — twice the effort for half the result. By comparison, pets can use about 1.5 times more of the nutrition in meat, egg and animal protein.

Animal protein also supplies amino acids (note 1) better matched to a pet's needs — taurine, one of the cat's essential amino acids (note 2), is something plants cannot provide. Research also shows that for the same weight of protein eaten, animal protein converts into more body weight — pets grow taller and stronger.

Which meats build muscle best? Meet BCAAs

Talk about muscle and you must talk about BCAAs — branched-chain amino acids — the three essential amino acids with a branched structure: leucine, isoleucine and valine.

Different amino acids build different proteins, like bricks of different colours and properties building houses of different functions: elastic muscle houses, thin tough skin walls, the multi-purpose liver factory. But dietary protein can't be used directly; the digestive organs break it into little amino-acid bricks and ship them to each organ.

The body is clever: it checks whether its owner is a couch potato, lives in the Arctic and needs lots of fat, is under heavy stress — and delivers the right kind and amount of bricks for the houses needed.

So what's special about BCAAs?

Ordinary bricks (amino acids) go first to the liver factory to be remodelled before being sent around the body, and only the surplus builds muscle houses. BCAAs skip the liver and go straight to the muscle.

When pets run and jump, the muscle house is squeezed and worn. Bricks arriving at the muscle slow the wear and help repair, making the muscle house bigger and better. Better still, when leucine reaches the muscle it acts like a foreman with a megaphone: "Your bricks are here — build it bigger!" So foods rich in BCAAs help cats and dogs grow and repair muscle during and after activity.

The table below compares BCAA content in common pet-food ingredients. At the same dry weight, compared with peas (the ingredient kibble most often uses to boost protein), the difference can be nearly five-fold.

BCAA content: plant vs. animal protein ▼

Unit: mg per 100 g dry weight, rounded. Source: Taiwan FDA Food Nutrition Composition Database.

The takeaway

Animal protein gives pets more complete nutrition and is easier for their gut to absorb and use. Its high-quality BCAAs feed muscle directly, improve exercise performance and are a key protein source for muscle synthesis — muscle up, fat-burning up, body condition upgraded.

When choosing your pet's food, look first at the proportion of animal protein and favour brands that pay close attention to amino-acid ratios.

Note 1: amino acids are the small molecules that make up protein; different amounts and kinds form different proteins. Note 2: essential amino acids are those the body can't make and must obtain from food; long-term deficiency causes health problems.

References

1. German A. Obesity in companion animals. In Practice 2010;32(2):42-50.
2. Mariotti F. Plant protein, animal protein, and protein quality. Vegetarian and Plant-Based Diets in Health and Disease Prevention. Academic Press, 2017:621-642.
3. Sarwar G, et al. Inter- and intra-laboratory variability in rat growth assays for estimating protein quality of foods. J AOAC 1984;67(5):976-981.
4. Brestenský M, et al. Branched chain amino acids and their importance in nutrition. J Microbiol Biotechnol Food Sci 2019:197-202.
5. Yin J, et al. Branched-chain amino acids, especially of leucine and valine, mediate the protein restricted response in a piglet model. Food Funct 2020;11(2):1304-1311.
6. Taiwan FDA Food Nutrition Composition Database.