This is true. I've been a size 10 all my life apart from when i've been pregnant. I don't 'diet' or deliberately restrict myself, but I just don't really eat that much.
After my third baby I needed to shift a stone so I tracked calories for six months and it came off no probs and has stayed off. Now I always have in the back of my head the rough calorie count for things so I sort of subconsciously keep track as I go along and I know what an excessive day of eating looks like in terms of my calorie allowance. For example, my TDEE is 1600 calories a day. One chocolate digestive is 100 cals, a banana is 100 cals, a fistful of fusilli pasta is about 100g, which is about 300 cals, two heaped dessert spoons of greek yoghurt is about 100g, which is about 140 cals, etc, etc.
I'll have a couple of slices of toasted homemade bread for breakfast with a small amount of proper butter and marmite, then a banana mid-morning, lunch will be something like soup, an omelette, or houmous and pitta bread with cut up veggies, then dinner will be homemade chicken curry, spag bol, or similar, but a normal portion. If I do snack in between it'll be something like greek yoghurt or a bag of sweet/salty popcorn , or a couple of slices of malt loaf.
I don't really have a sweet tooth so don't eat many cakes or biscuits. I only drink a couple of glasses of wine at the weekend, never drink fizzy drinks or squash, very rarely order takeaways (family of five = £70 at least!!). None of this feels like I'm depriving myself and I don't have to think about it when I'm doing it. But I suppose to people who do all those things, it would feel like deprivation and hard work.