There has been a recent upsurge in articles advising people how to lose weight "successfully", i.e. to lose weight and keep it off. There are discussions and theories about fructose in the diet, about insulin resistance, about the relative merits of the Ornish and Atkins diet, about stomach-banding operations, about the role of exercise and heredity, etc. But we still know far too little about how the body processes ingested calories of all kinds---fats, proteins, and carbohydrates.
What we do know is that the body has the enzymes necessary to interconvert carbohydrates and fats, protein and fats, and carbohydrates and protein, with the exception of the eight essential amino acids and the three necessary fats. We will assume an adequate intake of these latter two as well as sufficient daily vitamin intake, be it contained in the food eaten or taken as a daily supplement. And let us recognize that eating is like breathing, in that there is an involuntary autonomic drive, which can be overridden by voluntary means.
Not to be obvious, but we always have examples of people who are grossly overweight and dangerously underweight, viz. sumo wrestlers and anorectic patients (and I am not here going to discuss the distorted body images that are involved).
Let us first consider the marvelous caloric balancing act that the body does daily and therefore yearly without any conscious guidance. It is generally agreed that ingestion of approximately 3500 calories can be converted to one pound of flesh, and oxidation of one pound of flesh releases 3500 calories (remember that part of the food we eat daily is oxidized just to generate the heat needed to keep our body temperature fixed and comfortable). We also know that exercise generates heat, so that the body shivers when it is cold as a way of raising its temperature. Now there are about 350 days in a year, and if we divide 3500 calories by 350 days we see that the body must ingest fewer than 10 extra calories a day or burn it off in some manner if we don't want to gain weight. No one knows how the brain instructs the body to do this marvelous act, and yet most of us have weights that are fairly constant year to year, which means that the brain is micromanaging our caloric intake and expenditure in a way that we could not possibly do consciously. Could any of us eat the same amount of calories plus or minus 10 calories on a daily basis? I think not, no matter how committed we were. Remember that in a 2000 calorie daily diet, 10 calories is 0.5% of the daily allotment, and even if we had the will, we do not have the skill to measure the total daily calories we eat to an accuracy of 0.5%.
So how does one go about losing weight? The body has a fixed daily energy expenditure to keep your core temperature at 98.7 or whatever your normal temperature is. Then there is an additional energy expenditure, also gained by oxidizing food or flesh, for the motion of your muscles, both involuntary (e.g. heart and diaphragm) and voluntary, as in your skeletal muscles. That's it. So if we ingest more calories than are needed to be oxidized to supply our daily energy requirements we will gain weight, and if we ingest less, we will lose weight. In other words, there are two types of foods: too much and too little. (And once we solve the weight problem we can proceed further as to food pyramids and the like.)
At this point, I will give a small nod to the nutritionists, and add that the two most useless types of calories come in the form of white potatoes and white bread. Both have a high glycemic index, potato more than bread, and therefore stress your insulin-glucose system. No one on a diet should eat either of them, IMHO. The question of whether or not you should eat chocolate before your main meal so as to decrease your appetite and therefore eat less remains unanswered.
Now for the hard part: actual weight loss. There are myriads of suggestions out there including drinking water before meals, leaving the table before you feel full, eating smaller portions, drinking more caffeinated beverages, eating more fiber, taking diet pills, exercising more, etc. But the advice begs the question of actually losing weight. Besides feeling your clothes become looser, the only way to know if you have lost weight is to step on a scale. And I mean an old-fashioned scale, not a digital one which can have errors.
Weigh yourself today and then re-weigh yourself tomorrow, or in two days, or at least in seven days. If you have gained weight then eat less, and keep on eating less between successive weighings until you start to lose weight. Then just continue. So long as you eat fewer calories than your body burns, you will lose weight. It all comes down to a fuel-energy balance, which is why your car weighs more when you fill it up with gas and then steadily loses weight as you burn the gas in the tank and it is used up. If you find as most people do that exercise both makes you feel better from the endorphins it generates and helps you to lose weight by suppressing your appetite and burning off calories, then do it.If it helps you to make a daily food/calorie list, then do it. If it helps you to omit lunch (I never have lunch when I am at home) then do so.
Everyone has a different pattern for weight loss, just as everyone has a different need for sleep. We are all wired differently, but the iron laws of physiology (physics as applied to the body) tell us that fuel is either oxidized or stored, and the amount of fuel ingested is the ultimate determinant. And yes, people do have different fundamental metabolic rates, so that a diet that works for one person may not work for another.
And no one knows why everyone likes ice cream: I personally think that it is because it is similar in taste to frozen mother's milk: sugar and fat.