Is fat the most satiating macronutrient?

Satiety is very subjective, so it's hard to measure it precisely. Ditto that for determining dietary intake accurately in free-living people using dietary records. That said, in studies of high carbohydrate and intermediate carbohydrate diets compared to high fat diets, when comparing weight losses in the initial 3-6 months (when diet adherence is best), the high fat ketogenic diet usually delivers about twice the weight loss (Gardner, 2007; Shai, 2008; Forsythe, 2008). But perhaps the most convincing study was done by Dr. Guenther Boden in Philadelphia and published in the Annals of Internal Medicine in 2005. His team studied 10 overweight adults with type 2 diabetes in a metabolic ward for 3 weeks. For the first week, they ate to satiety from a carefully monitored buffet where everything they consumed was weighed. For the last 2 weeks, the buffet was changed to contain only low carb, high fat choices. For the first week, the patients remained weight stable eating about 3100 calories per day. For the next 2 weeks, they consumed only 2200 calories with protein intakes remaining about the same. And here’s the surprise—they reported significantly greater satiety eating the high fat diet at a much lower calorie intake.

Citations
  1. Boden G, Sargrad K, Homko C, Mozzoli M, Stein TP. Effect of a Low-Carbohydrate Diet on Appetite, Blood Glucose Levels, and Insulin Resistance in Obese Patients with Type 2 Diabetes. Ann Intern Med. 2005;142:403–411. doi: 10.7326/0003-4819-142-6-200503150-00006
  2. Forsythe CE, Phinney S, Fernandez ML, Quann EE, Wood RJ, Bibus DM, Kraemer WJ, Feinman RD, Volek JS. Comparison of low fat and low carbohydrate diets on circulating fatty acid composition and markers of inflammation. Lipids. 2008; 43(1): 65–77. doi: 10.1007/s11745-007-3132-7
  3. Gardner CD, Kiazand A, Alhassan S, Kim S, Stafford RS, Balise RR, Kraemer HC, King AC. Comparison of the Atkins, Zone, Ornish, and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal Women The A TO Z Weight Loss Study: A Randomized Trial. JAMA. 2007;297(9):969–977. doi:10.1001/jama.297.9.969
  4. Shai et al. Weight Loss With a Low-Carbohydrate, Mediterranean, or Low-Fat Diet. The New England Journal of Medicine. 2008;359:229-41. doi:10.1056/NEJMoa0708681