The first naturopath I saw, many years ago in Eugene, was a sveldt young woman who didn't appear to have an extra ounce of fat on her skinny body. She and I didn't last long as doctor/patient but I will always remember her insistence that dietary fat did not make one fat. "I", she said, "am a perfect example of that." Her diet included lots of fats.
Since then, I've heard the same theory in various places. The body needs a certain amount of fat in order to be healthy -- preferably in the form of healthy fats, of course. In my own life, I've never noticed that more or less fat in my diet led to more or less fat on my body.
My recent week-long stays at two monasteries with vastly different dietary styles led to an interesting, if unintentional, experiment with this subject.
In Austin, the diet was traditional Burmese: various meats and veggies swimming in heavy sauces floating with oil, lots of white rice, rice noodles and other noodles. No fresh veggies or salads.
At Bhavana, absolutely no fat is allowed in any food, per instructions from the abbot's cardiologist. The rest of us might get scrambled eggs (dry-scrambled), but he would have only the white of a boiled egg. There were nut butters and margarine available on the table, but I had only a small amount of almond butter a couple of mornings, and bread only once. There were plenty of fresh veggies and always a salad. There were two days of delicious food dana (food offerings brought in from outside). The first was 'normal' American foods brought by a woman whose cooking I'd been lucky enough to taste before -- this time no fats or oils used. The second was traditional Sri Lankan food, but without coconut milk or oil of any kind. All of it was delicious without fat.
So where would you guess I'd lose weight, and where I'd gain? I was certainly surprised! When I returned from Austin after 7 or so days of this delicious diet, I felt as if I must have gained weight -- but the scale said otherwise. I was down 2 or 3 pounds from 'average'. When I returned from 5 days of healthy, fat-free food at Bhavana, I was once more surprised -- up 2 or 3 pounds from 'average'. In between the two, my weight had returned to 'average' so both visits started at around the same figure.
More interestingly, I think I ate more in Austin, and I know I had really no exercise other than walking from place to place at the monastery. At Bhavana, I stood on my feet for 3 to 5 hours per day, working in the kitchen, washing up after meals, and doing another project assigned to me while I was there. And I didn't overeat.
I'm not sure what the conclusion is for this little experiment, other than that as I've noted in the past it doesn't seem to matter what I eat, how much I eat, or how much/little I exercise when it comes to gaining or losing weight. But this was certainly far more of a contrasting diet than any I would or could have devised at home. Make of it what you will.