Carbohydrate and sugar reductions seem like a very reliable way too. There are many anecdotes about successful weight loss on diets that allowed the person to "eat as much as they want" but had to limit their daily intake of carbohydrates.
1 bowl (2 cups of rice, about 330g, more or less 1 serving in areas where white rice is a staple food) have a 331 kcal [1] Even if one would ate a whole package of Canadian Bacon (6 oz, 139g) it would only be 257 kcal [2].
Carbs are very easy to gorge. A medium sized fast food cup of soda is 180kcal. Same cup for raw orange juice is 223kcal. For comparison 150g of beef is 274kcal and that would be a big serving (IMO).
When people cut carbs from their diets they end up cutting the most densely caloric food: pasta, rice, starch and sugar and that's a good thing too, even eating as much of the rest as they want they will hardly be able to overconsume calories.
[1] http://ndb.nal.usda.gov/ndb/foods/show/6497?man=&lfacet=&cou...
[2] http://ndb.nal.usda.gov/ndb/foods/show/2636?fgcd=&manu=&lfac...
Using reported calorie information is a physiological method, and appeals to those who prefer quantifying and tracking their everyday life. Carbohydrate reduction is (in this sense) a psychological method, and appeals to those who struggle with cravings and a lack of structure.