There was a study done in 1956 comparing weight loss on diets of differing macronutrient content. The diets were all 1,000 calories. One was 90% carbohydrate, another was 90% protein, another was 90% fat, with the last being a mixed diet. Those on the 90% fat diet lost the most weight, with those on the 90% protein diet coming in as a close second. Those on the 90% carbohydrate diet lost the least, and some of those even gained weight.
A. Kekwick M.A., M.B. Camb., F.R.C.P. , G.L.S. Pawan B.Sc. Lond. Calorie intake in relation to body-weight changes in the obese. The Lancet, Volume 268, Issue 6935, Pages 155 – 161, 28 July 1956.