Seems great doesn't it? No dieting, eat what you want, how ever much as you want - just eat 3 times per day at regular times, never after 6pm, and walk one hour per day.
Walking for an hour a day is going to help. Any extra activity that burns energy that you wouldn't have otherwise burnt is going to help you lose weight. Swimming, cycling, gardening, household chores, running, jogging, gym, football, cricket, kick boxing, etc etc - all are alternatives.
The problem with the method is that it is based on unsound judgment. The prisoners were subject to a lifestyle change, that made them eat regular meals, take regular exercise, etc. But they were probably subject to other factors ie. "obviously the more healthy your meals the more quickly you will lose weight". Portion sizes were probably also limited. Popping out to the pub or chip shop were almost certainly unlikely.
The sound advice in the method in my opinion are: change your lifestyle, eat a breakfast, take regular exercise, don't starve yourself.
But in addition, controlling portion size, eating good healthy foods, avoiding bad foods and drinks, controlling calorific consumption are also important for long term weight loss.