Long and boring story but my rescue girl was piling on the pounds and for complicated reasons including severe food anxiety and another cat I couldn't restrict the amount I gave her. She went from her ideal weight of around 4.5kg to over 6 and I was desperate. Eventually I found Hills reduced calorie foods, two kinds, Metabolic and r/d. Bought microchip feeders and within 8-10 weeks she was a much better shape. So far so good.
That was in April 2016. With some expensive wasteful experimenting we settled to r/d dry and metabolic pouch. That was the first mistake, the two work in different ways and should not be mixed, but that is not clear from any labelling. R/d is labelled for weight loss and should be used short term only, and that's in the small print but nothing about long term being bad. Metabolic claims to be "for weight loss and maintenance" which implies safe long term.
That was her regular diet for 18 months until November 2018, and then she suddenly became very ill. I call it her crash. Diarrhoea and vomiting, both yellow (suggesting liver or bile problems) and sudden dramatic weight loss down to 4.2kg and visibly thin, from slightly podgy, refusing all food for a couple of days, even tuna. I suspected hepatic lipidosis and off we went to the vets. Turns out she was hyperthyroid which was successfully treated with radioactive iodine and may have an underlying liver problem. She still has loose stools now. I had a hunch maybe the food might have been a problem and started researching.
I discovered that this diet food has extremely high levels of vitamin A, around 17 times the recommended amount in cat food and way more than any other Hills food. Vitamin A is fat soluble so excess is stored in the liver and becomes toxic over time, it's not an immediate poison. Although Molly doesn't have the symptoms of vitamin A toxicity, this high level over 18 months is not good, it's potentially dangerous. The level is about the same as in raw liver, which is how most cases of vitamin A toxicity happen.
Hills won't respond to my emails asking if this is a misprint or if there is a benefit to such high levels, so I asked my vet. She is a great vet but she was very dismissive about the evidence I presented to her, saying she was sure a reputable brand wouldn't put dangerous levels of anything in a pet food. I know this food is effective for weight loss and I'm sure it's safe short term but I'm very uncomfortable about their labelling and warnings about long term use, with this high level of vitamin A.
The good news is Molly's guts are still gradually getting better - still some days of soft stools and some days hard but no yellow or orange colour for over a month now, a year on from taking her off this food. Her hyperthyroidism is cured and her liver enzymes are still raised but coming down. Her slightly raised kidney function values post treatment are also coming down. And she is a little overweight from ideal but not in the obese high risk zone for diabetes and heart disease.
Please read any small print in feeding guidelines carefully and if possible check nutritional information against recommendations whenever possible, you can ask manufacturers for this for any food but Hills publish it on their website. This is one source of recommended nutrient data but there are others. http://dels.nas.edu/resources/static-as ... _final.pdf
Caution with Hills diet food
Re: Caution with Hills diet food
Thanks for the heads up. It's a bit worrying that your vet was so glib about the readily accepted reliability of quality foods. But is does reinforce the importance of speaking to your vet when trying to fit diet to multiple health issues, when some treatments/diets may be bad for other conditions, or when the combined effect results in potentially harmful imbalances.