To determine how to feed our dogs we must first determine their natural diet. Although a body of research exists that claims dogs’ omnivorous disposition, it ignores the evolutionary and biological evidence that underscores dogs’ carnivorous nature.
The evolution of the domestic dog hints at dogs’ carnivorousness. Humans domesticated dogs between 27,000 and 40,000 years ago. Anywhere within this range is not enough time for dogs to have evolved away from a carnivorous diet. Similarly, this range coincides with prehistoric humans — that is humans before the agricultural revolution, which began roughly 12,000 years ago. Dogs therefore evolved for more than half of their existence alongside hunter-gatherers, who primarily ate meat, not agriculturists.
This evolutionary evidence reconciles with important genetic and anatomical clues. Domestic dogs share approximately 99.8% of their DNA with wolves and 96% with coyotes. Both wolves and coyotes are carnivores. Dogs fall in between them genetically. Anyone wanting to prove that dogs are not carnivores would need to discover how they are excepted from this spectrum. Outside of a few, very narrow, examples, no one has done so.
The anatomy and biology of dogs also underscores their carnivorous disposition. Dogs have the same digestive systems as their feral, carnivorous, cousins. Dogs also share a number of other traits primarily unique to carnivores: panting, instead of sweating, to cool; lapping, instead of sipping, to drink; producing their own vitamin C, instead of consuming it; and, claws in lieu of hands or hooves. Despite these overwhelming physical and behavioral signs, a number of researchers argue over the debatable position that since dogs can digest carbohydrates, they must be omnivorous.
This analysis, however, not only assumes that digestibility of a food alone determines its appropriateness in a diet, but also ignores the metabolic efficiency of that food once digested. Certain foods can be both digestible and biologically inappropriate. Such foods can lead to persistent hormonal imbalances that drive chronic conditions. Recent research shows that most chronic diseases in dogs such as kidney, liver and cardiovascular disease, as well as diabetes and arthritis, to name a few, cluster around obesity.
If your dog isn’t obese, he or she is much more likely to be healthy. Dogs fed a carnivorous diet do not become obese. Lean dogs metabolize their food efficiently because they do not have unnaturally high levels of the hormone insulin constantly circulating through their bloodstreams. Grains and sugars, though arguably digestible, are metabolically inefficient for dogs and raise insulin, thus driving obesity and illness.
Finally, proponents of the omnivorous dog ignore the observation that dogs fed carnivorously are on balance much healthier than dogs fed omnivorously. Common sense dictates that whatever diet produces the healthiest dogs is the natural diet of dogs – the starting point of our inquiry. But the science alone obviates the need for common sense.
 Skoglund, P., E. Ersmark, E. Palkopoulou, L. Dalén. 2015. “Ancient Wolf Genome Reveals An Early Divergence of Domestic Dog Ancestors and Admixture Into High-Latitude Breeds”. Current Biology. Jun. 25(11): 1515–19. (http://www.cell.com/current-biology/abstract/S0960-9822(15)00432-7).
 See generally, Diamond, J. 1999. Guns, Germs, and Steel: The Fates of Human Societies. (New York: Norton).
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 Landry, S.M., H.J. Van Kruiningen. 1979. “Food Habits of Feral Carnivores: A Review of Stomach Content Analysis.” Journal of the American Animal Hospital Association. Nov./Dec. Vol. 15: 775.
 See, for example, Axelsson E., et al. 2013. “The Genomic Signature of Dog Domestication Reveals Adaptation to a Starch-Rich Diet.” Nature. (495): 360-364. (http://www.nature.com/nature/journal/v495/n7441/full/nature11837.html).
Strong carnassial teeth, simple stomachs of great digestive capability, thickly muscled esophaguses, stomachs, and intestines, residual cecae, and simple non-sacculated colons.
Roberts, W.C. 2000. “Twenty Questions on Atherosclerosis.” Proceedings (Baylor University. Medical Center). Apr. (13)20: 139–143.
 Axelsson, et. al.
 See, for example:
German A.J., S.L. Holden, T. Bissot, R.M. Hackett, and V. Biourge. 2007.“Dietary Energy Restriction and Successful Weight Loss in Obese Client-Owned Dogs.”Journal of Veterinary Internal Medicine. Nov./Dec. 21(6): 1174–80. (http://www.ncbi.nlm.nih.gov/pubmed/18196722).
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Kealy R.D., D.F. Lawler, J.M. Ballam, S.L. Mantz, and D.N Biery, E.H. Greeley, G. Lust, M. Segre, G.K. Smith, and H.D. Stowe. 2002.“Effects of Diet Restriction on Life Span and Age-Related Changes in Dogs.” Journal of the American Veterinary Medical Association. May 220(9): 1315–20. (http://www.ncbi.nlm.nih.gov/pubmed/11991408).
Rawitscher, R.E., W.S. Gardner, and W.H. Muller, Jr. 1973. “Experimental Canine Coronary Atherosclerosis.” Annals of Surgery. Mar. 177(3): 357-61. (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1355540/pdf/annsurg00253-0109.pdf)
Tvarijonaviciute et al. 2012. “Obesity-Related Metabolic Dysfunction in Dogs: A Comparison with Human Metabolic Syndrome.” BMC Veterinary Research. Aug. (8): 147-55. http://www.biomedcentral.com/1746-6148/8/147.;
Tvarijonaviciute et al. 2013. “Effect of Weight Loss in Obese Dogs on Indicators of Renal Function or Disease.” Journal of Veterinary Internal Medicine. Jan./Feb. (27)1: 31-8. (http://onlinelibrary.wiley.com/doi/10.1111/jvim.12029/full).
Weeth, L.P, et al. 2007.“Prevalence of Obese Dogs in a Population of Dogs With Cancer.” American Journal of Veterinary Research. 68(4): 389-98.
Yamka R.M., K.G. Friesen, and N.Z. Frantz. 2006. ”Identification of Canine Markers Related to Obesity and the Effects of Weight Loss on the Markers of Interest.” International Journal of Applied Research in Veterinary Medicine. 4(4): 282–92.
 Rothwell, N.J., and M.J. Stock. 1981. “Thermogenesis: Comparative and Evolutionary Considerations.” In Cioffo, James, and Van Itallie, eds., 1981, 335-44.
 See, for example:
Berson, S.A. and R.S. Yalow. “Insulin ‘Antagonists’ and Insulin Resistance.” In Diabetes Mellitus: Theory and Practice, ed. M. Ellenberg and H Rifkin (New York: McGraw-Hill), 388-423. (1970).
Gordon, E.S. 1970. “Metabolic Aspects of Obesity.” Advances in Metabolic Disorders. 4: 229– 96.
Gordon, E.S. 1970 1969. “The Metabolic Importance of Obesity.” In Symposium on Foods: Carbohydrates and Their Roles, ed. H. W. Schultz. Westport, Conn.: Avi Publishing, 322– 46.
Taubes, G. 2007. Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight-Control, and Disease. (New York: Random House), 178-185.