- eat fewer carbs, especially sweets and sugary drinks
- eat less veggie oil (i.e. chips or other fast food that's been fried, mayo made with veggie oil, etc)
- eat more saturated fat and eggs, these are good for avoiding liver problems (e.g. if you drink alcohol)
- use up and down days, hardly anyone can stick to a diet every day
- eat less often, 2 meals a day is enough
- long gaps between meals, i.e. no/few snacks
Getting fatter is all about more calories going into your fat cells and less calories coming back out, these measures all aim to improve that balance.
Eating carbohydrates increases the amount of glucose in your blood, which increases the amount of insulin in your blood, which tells your fat cells to store food. (High insulin levels probably aren't good for your arteries or for cancer either.) One potato or a small amount of rice is probably no big deal, but I try to avoid sweet drinks, large sweet puddings, or eating lots of fruit.
Protein intake doesn't give a lot of calories, so that means I try to eat plenty of fat. I do that by using fatty sources of protein, and I try to use added fat with any carbs I eat - I think of it as a bit like the French approach; not too much bread, but with plenty of butter :)
Unsaturated fats help keep you sensitive to insulin. This means your fat cells keep storing food, which means you get fatter. In the long run, this is bad for your health. (Veggie oils tend to contain lots of omega-6 fatty acids too, which are also very unhealthy.) I suspect the widespread use of veggie oils in packaged food, fast food and restaurant food is one of the biggest problems with our modern diet (and in medical use).
Eggs and Saturated Fat
These used to be thought to be bad for you, but views are gradually changing nowadays as the science is understood better and old thoughts are discredited. Eggs and saturated fat are good for your liver, which is important if you're fat, in your 50s and like a drink. Some good sources of saturated fat are beef, lamb, full fat dairy, and coconut oil (an exception to the veggie oil suggestion above). They're also very filling, which is useful if you're trying to eat less.
Up and Down Days
Hardly anyone can stick to a diet every day, it's just not realistic. So I aim to eat more on some days and less on others. This might be up/down every other day, or just 2 really low "fast" days a week, or 2 big "cheat" days at the weekend. Whatever seems convenient at the time.
The point is, it is ok to miss a meal occasionally, in fact it's probably good for you. Eating twice your normal daily amount probably isn't good for you, especially if you do it every week, but eating a little more because ... you want to! ... is ok as long as you're eating a bit less on other days.
So I don't try to stay deadly accurate with my daily calorie intake, that way lies madness. I figure it's ok to eat say 1000 calories one day and then 3000 the next, if I'm aiming for a 2000 average. 1000 calories or less doesn't sound like much, but it's only one day.
Two Meals a Day
Insulin levels in your bloodstream rise after nearly every meal, which stops most fat-burning that might have been happening. If you only eat 2 meals a day, there is more chance of burning some fat between meals. I don't think the timing matters too much, you either get a nice long fast overnight, or two shorter gaps, one after each meal. Even eating just one meal in a day can be ok, particularly if it's a "down" day when you're trying to eat fewer calories.
Fewer/No Snacks Between Meals
Like meals, snacks will tend to raise insulin levels, stopping most fat burning. I try and keep any snacks to between my two meals (I generally eat breakfast quite late), so I still get the benefit of a long overnight fast. If I do snack I just view it as a smaller version of what I used to eat as a 3rd meal.
Extra thoughts; wherever possible, eat "real food", not something from a packet with a huge ingredients list. And doing some kind of mild exercise, even just a 10 minute walk, sometime in the first hour or so after a meal is good for reducing glucose and insulin levels in your blood.
Of course, this is just my understanding, which could easily be
wrong, and is a simplified view roughly describing what I aim for
personally. We're all different in our genes / history / goals / priorities, so some of these ideas may not be useful to you. But hopefully some of them are :)