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Fat Loss Supplements for Pets

The last blog introduced Omega-3 fatty acids as a weight loss aid in pets. Weight loss supplements are well known in human weight loss but less utilized in pets. In addition to Omega-3s there are some other proven weight loss supplements. This post will discuss those supplements and list others that are purported to be effective aids but lack the scientific evidence to support such claims.



L-Carnitine is an amino acid like molecule that enhances the uptake of fatty acids into the mitochondria for energy production. Body cells produce energy by burning sugars, proteins and fats. Sugars can produce immediate energy without the need of oxygen. This can happen anywhere in the cell. For longer, more sustained energy, the body uses fats and proteins for energy but needs the cellular organ known as the mitochondria to do this. L-Carnitine is needed to shuttle fats from the body of the cell into these mitochondria. Studies in humans and animals have confirmed that subjects on a calorie restricted diet lose more weight if they are supplemented with L-Carnitine to facilitate this fat usage. This is an extremely safe and effective supplement that is readily available at markets, health food stores and pharmacies. Consult your veterinarian for a dosage for your pet.


L-Arginine is another amino acid-like chemical. The veterinary community has yet to recognize its potentials, so studies are lacking in cats and dogs. An initial study in obese mice documented a 16 percent weight loss in ten weeks without calorie restriction. Abdominal fat was reduced by 45 percent. Fat energy utilization increased 22 percent and sugar energy utilization increased 34-36 percent. Abnormalities associated with diabetes also improved. Further studies in obese rats, pigs and humans confirmed these results. All studies documented an increase in muscle tissue of supplemented subjects.

Such findings offer promise for owners who are frustrated with weight loss in their pets, and could prove very helpful for pets needing to lose only a few extra pounds or for whom calorie restriction is difficult. Toy and small breeds are obvious candidates. Animals with diseases that could be complicated by calorie restriction would also be great candidates for L-Arginine supplementation. Again, consult your veterinarian for an appropriate dose.


Dehydroepiandrosterone, or DHEA, is a steroid hormone involved with the production of testosterone and estrogen sex hormones. Studies have documented increased weight loss in calorie restricted weight loss patients receiving this supplement. The increase in sex hormones and their potential health side effects were of concern to the researchers in these studies. This supplement should be used with extreme caution and only under the supervision of a veterinarian.

Dirlotapide or Slentrol

Dirlotapide is a pharmaceutical drug that inhibits the transfer of dietary fats from intestinal cells into the blood stream. The accumulation of fat in the intestinal cells is thought to increase the release of intestinal hormones that signal fullness or satiety in the brain, reducing appetite. Four studies have documented that dogs being supplemented with dirlotapide lost 9.5-15 percent more weight than non-supplemented controls. Supplemented dogs did experience a 2.5-3.5 percent weight regain when dirlotapide was discontinued, however. Dirlotapide is only approved for use in dogs and is only available through veterinarians or a veterinary prescription.

Supplements Without Documented Effective Results

Conjugated Linoleic Acid, or CLA, is an omega-6 fatty acid without the documented results of the omega-3s. Chromium picolinate is widely touted as a "fat burning" aid in humans. There is no evidence to suggest that it is helpful in pets and DNA damage has been documented with its use. Starch blockers have proven to be useless in humans and animals. Chitosan, a compound from the shell of crustaceans, vitamin A, soy protein, flaxseed, and tamarind (a fruit) are often cited as diet aids without any scientific substantiation.

Ephedra, found in teas and other Chinese herbs as well as in caffeine, have been advocated as weight loss supplements. In addition to lack of evidence of effectiveness, these compounds can be very toxic to pets. Psyllium, the active ingredient in Metamucil, guar gum, spirulina, dandelion, casacara plant extracts and ginseng have all been promoted as weight loss supplements — without any scientific evidence to back the claims.

Bottom Line

There is no magic supplement solution to weight loss. Calorie restriction is the key. The aids like L-Arginine, L-Carnitine, Omega-3s and Dirlotapide may help, but weight loss requires commitment to a weight loss plan and, ultimately, a lifestyle change that includes a more appropriate feeding program along with consistent exercise.

Dr. Ken Tudor

Image: Javier Brosch / via Shutterstock

Comments  6

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  • More is Not Better
    05/03/2012 07:15am

    With humans and critters, some humans will assume that if a little bit is good, more must be better. Obviously this isn't necessarily true because overdoing these things might well cause harm.

    And just because something can be found at the health food store doesn't mean it's completely safe or effective.

    Excellent info, Dr. Tudor. Thank you!

  • Herpes interactions?
    05/03/2012 10:23am

    L-Lysine is often given to cats (and I presume dogs) with herpes infections. It works by reducing the amount of L-Arginine (or the ratio), I believe. L-Arginine is food for the herpes virus.

    I would think that L-Arginine would be detrimental to a critter with herpes, and would probably negate the benefits of Lysine.

    Unfortunately, the cat I have most in need of weight loss help is also a herpes cat.


  • Kalynnda
    05/03/2012 11:24pm

    You are right that L-Arginine is not a good choice for a herpes cat. But a serious weight loss program with L-Carnitine is a great strategy for any cat, herpes or not. In fact L-Carnitine has been shown to be preventative to the development of the hepatic lipidosis that can occur when calorie restricting cats.
    Dr. T

  • Another great one
    05/04/2012 04:39pm

    Thanks, Dr. Tudor. This is more really helpful information.

    I will talk with my regular vet about these supplements.

    I talked with my rehab. vet, who has been tracking my dog's weight for 5 months, and we found that he has been losing weight, but extremely slowly (which I suppose is good!). He's losing weight at probably about 1/2 lb per month.

    I must have his calories and exercise calculated to perfection ... for weight maintenance, rather than loss!

    My regular vet may be able to help me in adding these supplements to help step it up a bit.

    Thanks, once again!

  • Hepatic Health dog food
    01/01/2013 12:25am

    Dr Tudor,

    My dog is on a prescription dog food with both L-Carnitine and L-Arginine in it. It is supposed to be better for her because she has liver enzyme problems, and is labeled to promote liver health. She's been on it 6 months and has lost 9 of her 43 pounds and is now very sick with bloody diarrhea. Could these amino acids be causing it?

  • Katie
    01/01/2013 02:47pm

    Unfortunately bloody diarrhea is not a specific symptom for any particular abnormality. It is difficult to say whether these symptoms are related to diet, dietary components, other metabolic disorders, more specific gastrointestinal problems or even stress. Start with a veterinary exam and consultation for the most likely cause in your dog's case and then proceed based on veterinary recommendations.
    Dr. T

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