We have all heard of BMI (body mass index) – even if we weren’t sure what it stood for – we know it has to do with our body weight. It indicates what is considered to be a healthy weight based on your height and age. In animals we use the term BFI (body fat index) to determine how over (or under) weight a pet is. The calculations are based on weight and specific measurements across the body to determine ideal body size.
We often don’t think of our pet being overweight when we are told they need to drop about 5 lbs. We think – 5 lbs?, that’s it? – that isn’t very much at all. Well it is true that 5 lbs isn’t much… on a adult human body that weighs over 120 lbs. However 5 lbs on a dog that weighs only 30 lbs is about 20% of their total body mass. Think of that on the average adult human. Let’s say the adult is 145 lbs, 20% is 29 lbs! Now that seems like a fair bit, doesn’t it?
To give an even better perspective let’s take a look at our Biggest Loser Contestants. In this chart it shows each contestants weight, ideal weight, what that equates to in terms of BFI and how much weight they need to lose to reach an ideal weight. Ideal weight is considered to be a BFI in the 20% range (from 16-25%) in both cats and dogs.
| Contestant | Starting Weight | Ideal Weight | Current BFI | Lbs to Lose |
| Jojo | 4.3 kg / 9.5 lbs | 2.4 kg / 5.3 lbs | 55.0% | 4.2 |
| Poko | 9.6 kg / 21.1 lbs | 5.4 kg / 11.9 lbs | 54.6% | 9.2 |
| Piper | 8.5 kg / 18.7 lbs | 4.4 kg / 9.9 lbs | 57.8% | 8.8 |
| Gunner | 20.2 kg / 44.4 lbs | 11.4 kg/ 25 lbs | 54.6% | 19.4 |
| Lucky | 9.1 kg /20 lbs | 5.7 kg / 12.5 lbs | 47.4% | 7.5 |
| Playdoh | 5.7 kg / 12.5 lbs | 4.6 kg / 10.1 lbs | 35.0% | 2.4 |
| Aspen | 38.6 kg / 85 lbs | 23.6 kg / 52 lbs | 50.9% | 33 |
Now let’s look at these BFI’s on a human adult. This chart shows how much an average adult male would weigh if he were the same BFI percentage as the animals above and how much he would need to lose to get back to the healthy weight.
| Healthy Adult Male | OverWeight | Lbs to Lose | |
| 83.5 kg / 183.7 lbs | if 55% BFI then –> | 148.6 kg / 327 lbs | 143.3 |
| 83.5 kg / 183.7 lbs | if 54.6% BFI then –> | 147.2 kg / 323.8 lbs | 140.1 |
| 83.5 kg / 183.7 lbs | if 57.8% BFI then –> | 158.4 kg / 348.5 lbs | 164.8 |
| 83.5 kg / 183.7 lbs | if 54.6% BFI then –> | 147.2 kg / 323.8 lbs | 140.1 |
| 83.5 kg / 183.7 lbs | if 47.4% BFI then –> | 127 kg / 279.4 lbs | 95.7 |
| 83.5 kg / 183.7 lbs | if 35% BFI then –> | 102.7 kg / 226 lbs | 42.3 |
| 83.5 kg / 183.7 lbs | if 50.9% BFI then –> | 136.8 kg / 299.6 lbs | 115.9 |
Let’s look at a couple cross comparisons: Jojo is at a BFI of 55% and ideally should weigh 5.3 lbs, she needs to lose 4.2 lbs to get to her ideal weight. The same BFI in an adult male who should ideally weigh 184 lbs, would need to lose 143 lbs to achieve that goal. The 2.4 lbs that Playdoh needs to lose is equal to this adult male needing to lose 42.3 lbs – and in both cases that puts this male at a BFI of 20%, which in humans is actually still quite high. Really this male would need to lose even more weight to reach what is considered a healthy BMI comparable to the equivalent healthy BFI in your pet.
Now let’s look at some food comparisons (provided by Hill’s Pet Nutrition): 
Did you know that for a 10 kg (22 lb) dog, 1 small oatmeal cookie is the caloric equivalent of 1 hamburger or 1 entire chocolate bar for a 5’4″ person?
How about if a 5 kg (11lb) cat ate just one 28 gram cube of cheddar cheese? That would be the same as if a 5’4″ person ate 3 1/2 hamburgers or 4 whole chocolate bars!
What about if a 5’4″ person ate 3 hamburgers or 2 whole chocolate bars? That would be the same as a 10 kg (22lb) dog eating just 1 hot dog!
Now what about that 5 kg (11 lb) cat again – what if he ate 1 whole potato chip or drank an 8 ounce glass of milk? That would be the equivalent of a 5’4″ person eating 1/2 a hamburger or 1/2 a chocolate bar for the chip or 4 1/2 hamburgers or 5 chocolate bars for that glass of milk.
It isn’t uncommon for us all to think – awe it is just a little treat. It can’t hurt, and maybe if it only happened that rare once in a while, it wouldn’t be so bad, however, we need to remember to think of everything in terms of the lesser size our pets are compared to us. If they are only 1/5 our size (or even less) than that treat that seems small to us, is probably really big for them.
There are certainly health risks that go along with an unhealthy weight. As the body fat increases, so to does the risk for both cats and dogs on:
- Shortened life expectancy
- Diabetes
- Reduces mobility
- Arthritis
- Increased physical injury
- Respiratory disease
- Kidney disease
- Cancer
- Pancreatitis
and also for cats is an increased risk for:
- Hepatic lipidosis (Fatty liver which can lead to liver failure)
- Bladder stones
Now you are probably wondering how you can assess your pet at home to know if they are in the healthy range or heading their way towards unhealthy. The images (provided by Hill’s Pet Nutrition) below show how your pet looks physically and how that corresponds with each BFI value.
| Dogs | Ribs | Shape from Above | Shape from the Side |
| 20 | Slightly prominent, easily felt, thin fat cover | Well proportioned lumbar waist | Abdominal tuck present |
| 30 | Slightly to not prominent, can be felt, moderate fat cover | Detectable lumbar waist | Slight abdominal tuck |
| 40 | Not prominent, very difficult to feel, thick fat cover. | Loss of lumbar waist, broadened back | Flat to bulging abdomen |
| 50 | Not prominent, extremely difficult to feel, very thick fat cover. | Markedly broadened back | Marked abdominal bulge |
| 60 | Not prominent, impossible to feel, extremely thick fat cover. | Extremely broadened back | Severe abdominal bulge |
| 70 | Unidentifiable, impossible to feel, extremely thick fat cover | Extremely broadened back, bulging mid-section | Very severe abdominal bulge |
| Cats | Ribs | Abdomen | Shape from Above | Shape from the Side |
| 20 | Prominent, very easy to feel | Loose abdominal skin, easy to feel abdominal contents | Marked hourglass | Moderate to slight abdominal tuck |
| 30 | Not prominent, easy to feel | Loose abdominal skin with minimum fat, easy to feel abdominal contents | Slight hourglass/lumbar waist | No abdominal tuck |
| 40 | Not prominent, can feel | Obvious skin fold with moderate fat, easy to feel abdominal contents | Lumbar waist | Slight abdominal bulge |
| 50 | Not prominent, difficult to feel | Heavy fat pad, difficult to feel abdominal contents | Broadened back | Moderate abdominal bulge |
| 60 | Not prominent, extremely difficult to impossible to feel | Very heavy fat pad; indistinct from abdominal fat, impossible to feel abdominal contents | Severely broadened back | Severe abdominal bulge |
| 70 | Unidentifiable, impossible to feel | Extremely heavy fat pad; indistinct from abdominal fat, impossible to feel abdominal contents | Extremely broadened back | Very severe abdominal bulge |
One thing for us to remember is that our pets are certainly smaller than us and a little is really a LOT for them. Reducing their weight even just a little towards the healthy ideal can go a long way in improving your pet’s quality of life and reducing their risk factors for certain health conditions.
If you have concerns about your pets weight, give us a call. There are diets that are specifically designed to help your pet lose the weight without you feeling like you aren’t feeding them at all. Many of our staff are trained nutrition counsellors and are here to assist you.
