True, but not everyone knows that. They'll freak out at their pet's diagnosis and feed what the vet's office sells, and might back away from feeding real healthy food if the vet convinces them it's a bad idea. Having the option of a holistic prescription food that their vet won't fight them on could help out a lot of pets who would otherwise be subjected to the Gwainy Cwap.

Such a huge debate on something so simple. No matter what you choose to feed, the bottom line is Kcals. The fewer Kcals the more weightloss. Same as people, if you put more calories in than are burned there will be weight gain. If you put less calories in then there will be weightloss. The biggest problem we see is over feeding treats and free feeding. The only thing you have to remember with cats is that they have to lose weight very slowly. No more than 0.5% a month. I have seen it take as long as 2 years to safely get a cat back to optimal weight. The reason is that cats which lose weight too fast are at risk for a disease called hepatic lipidosis, a potentially fatal disease.

Interesting Reading from JAVMA (2002):
http://www.avma.org/publications/default.asp  (http://home.earthlink.net/~jacm2/id1.html)
•   CHO = complex carbohydrate = corn, wheat, rice, oats, rye, barley = these are all starches. Other starches – tapioca, potato
•   NFE is the difference:  100 – water – crude protein – Ether Extract (fat) – Crude Fiber – Ash (minerals) = NFE Starches, sugars & all soluble carbohydrates
•   One dietary factor that is receiving increased attention in obese cats is the role of CHO-dense diets. Cats housed exclusively indoors and consuming energy-dense, high-starch, dry foods are provided with more energy than they can effectively use. Any dietary CHO not used for energy is converted and stored as fat. Diets that are severely restricted for energy (eg, traditional low-fat, high-fiber, weight-loss diets) may result in weight loss, but it is often to the detriment of lean body mass.41,d Many of these diets contain high concentrations (> 15%) of insoluble fiber, which increases fecal bulk and volume, potentially increases fecal water loss (eg, increase risk of dehydration in cats not consuming an adequate quantity of water), and has detrimental effects on nutrient (eg, protein) digestibility.42,43 Ultimately, successful weight loss requires maintenance of lean body mass, because lean body mass is the major determinant of basal energy metabolism and is a major influence on whether weight is regained.44
•   Several investigators have evaluated the use of a high-protein, low-CHO diet (protein, 45% or higher; nitrogen free extract [NFE], < 10%; energy, 3,030 kcal of metabolizable energy [ME]/kg of food on an as-fed basis) for weight loss in cats. In one study, weight reduction in cats on a high-protein, low-CHO diet was compared with that for cats fed a commercial hypoenergetic diet (protein, 34%; NFE, 45%; energy, 2,600 kcal of ME/kg of food on an as-fed basis). Cats in both groups lost weight, but cats consuming the high-protein, low-CHO diet maintained lean body mass during weight loss. Additional studies are necessary, but this approach to inducing weight loss in cats makes metabolic and nutritional sense providing that they are fed appropriate amounts of food (ie, food is not available free choice).
•   Canned foods generally are best to provide a high-protein, low-CHO dietary combination. Most dry foods are energy dense and have greater CHO concentrations (CHO > 25% on a dry-matter [DM] basis), because starch is necessary to make the kibble. The typical nutrient characteristics of canned foods formulated for kittens are 45 to 55% protein (DM basis), 8 to 15% starch (DM basis), and 15 to 25% fat (DM basis) with little dietary fiber (< 1% [DM basis]). These characteristics are not far removed from that of the natural diet of cats (Appendix 1).

Notes from 2003 AVMA convention – The ‘catkins’ diet
http://www.catnutrition.org/catkins.html
•   So what's Dr. Greco's ideal cat food diet? She recommends a wet food, high in protein, high in fat, and low in carbohydrates. It's basically a "CatKins" diet, much like the Atkins diet popular today. This diet is going to keep a cat slim and help it avoid diabetes

J Feline Med Surg. 2006 Apr;8(2):73-84. Epub 2005 Nov 7.  Comparison of a low carbohydrate-low fiber diet and a moderate carbohydrate-high fiber diet in the management of feline diabetes mellitus.Bennett N, Greco DS, Peterson ME, Kirk C, Mathes M, Fettman MJ. Department of Clinical Sciences, Colorado State University, Fort Collins, 80523, USA. nbennet@colostate.edu   
•   This study compared the effects of a moderate carbohydrate-high fiber (MC-HF) food and a low carbohydrate-low fiber (LC-LF) food on glycemic control in cats with diabetes mellitus. Sixty-three diabetic cats (48 male castrated, 15 female spayed) were randomly assigned to be fed either a canned MC-HF (n = 32) food or a canned LC-LF (n = 31) food for 16 weeks. Owners were blinded to the type of diet fed. CBC, urinalysis, serum chemistry panel, fructosamine concentration and thyroxine concentration were determined on initial examination, and a complete blood count, serum chemistry panel, urinalysis and serum fructosamine concentration were repeated every 4 weeks for 16 weeks. Insulin doses were adjusted as needed to resolve clinical signs and lower serum fructosamine concentrations. Serum glucose (P = 0.0001) and fructosamine (P = 0.0001) concentrations significantly decreased from week 0 to week 16 in both dietary groups. By week 16, significantly more of the cats fed the LC-LF food (68%, 22/31), compared to the cats fed the MC-HF food (41%, 13/32), had reverted to a non-insulin-dependent state (P = 0.03). Cats in both groups were successfully taken off of insulin regardless of age, sex, type of insulin administered or duration of clinical disease before entering the study. There was no significant difference in the initial or final mean body weights or in the mean change in body weight from week 0 to week 16 between dietary groups. Diabetic cats in this study were significantly more likely to revert to a non-insulin-dependent state when fed the canned LC-LF food versus the MC-HF food.
Nutrition.org - 2004 The American Society for Nutritional Sciences J. Nutr. 134-2068S "Carbohydrate Malabsorption Is a Feature of Feline Inflammatory Bowel Disease But Does not Increase Clinical Gastrointestinal Signs".   

PubMed - J Nutr 2004 Aug; 134( "Canine and feline diabetes mellitus: nature or nurture?"•   Type 2 diabetes is the most common form of diabetes in cats. Evidence for genetic factors in feline diabetes includes the overrepresentation of Burmese cats with diabetes. Environmental risk factors in domestic or Burmese cats include advancing age, obesity, male gender, neutering, drug treatment, physical inactivity, and indoor confinement. High-carbohydrate diets increase blood glucose and insulin levels and may predispose cats to obesity and diabetes. Low-carbohydrate, high-protein diets may help prevent diabetes in cats at risk such as obese cats or lean cats with underlying low insulin sensitivity.

TBOBINA-
Has your cat had bloodwork done yet?  To help with the urine sample you could add some water to her wet food.  I do this with all my cats, and I have one who recently had a UTI& kidney infection and showed early CRF in the bloodwork.  I feed this cat Natura California Nautural wet because I don't trust other companies and haven't found anything else so far.  She was eating a different food even higher in phosphorous when I noticed she was becoming sick.  Despite the phosphorous content of the california natural I decided to use it over the prescription foods and see how she does with retesting blood test levels.  I think you will have a better idea of what direction to go in with food once you have the tests done.  Good luck getting the urine done- would you be able to remove the litter box for a few hours before the visit?  I've done that along with adding water to the food and it went fine.
Lanie

Wow, I haven't checked this site in a few weeks, and here is Karen STILL arguing that weight loss is not related to calorie intake, but only to eeevil carbohydrates.

Is the world flat too?  Should I start a thread titled "Gravity - just a marketing ploy designed to sell shoes", or "I forget - How many days does it take the sun to circle the Earth?"

It would be amusing, (and I have been amused by your posts), if it were not scary to think of pet owners being mislead by your blather.   Why don't you READ some of the links you have posted, and think about what they are saying?   

You keep confusing two concepts - cats get diabetes, and cats get fat.  Do fat cats get diabetes, does obesity contribute to incidence of diabetes - absolutely, no doubt.  Are most of these cats fat/diabetic due to eating high quantities of dry/high carb cat foods - well, yes, because that is what MOST people feed their cats, on a free choice basis, and cats do have different enzyme systems.  No one is disagreeing with this. 

BUT - Can a cat get fat from eating too much high protein, high fat, zero carb food - YES!!!   Otherwise, why would portion control be mentioned in your links?  Does a diabetic cat instantly lose weight if put on a low carb diet that regulates its diabetes - NO - as the study you have posted has reported.  A fat cat still needs calorie control to lose weight, regardless of the diet, regardless of whether or not it has diabetes. 

LOWER calories, from a LOWER fat diet will give better weight loss results.  Research shows that YES, higher protein diets are more effective because they maintain lean body mass. 

But the bottom line is - as Arabiannikki has tried again to explain - more calories in than out = fat cat, regardless of the composition of the calories.  There are better/worse choices, but removing carbs does not magically equal diet cat food. 

And people wonder why the U.S is a country full of fat people.      

BTW - you do realize that Dr. Greco now works for PURINA, right?  And that the vast majority of the diabetes cat research you all love to quote was originally funded by Purina too? 

I will check back in July to see what other scientific facts you have overruled using Google and PubMed.