Right,if anybody would like to hear the opinion of an actual Spanish woman (me!) who has been living in the UK, here it goes:
People in the UK DO have very strange ideas about nutrition and are obsessed with dieting. That was actually the first thing I noticed when I arrived. That, and how bloody difficult it was to find raw vegetables, healthy meats and oils in the supermarkets. British people think butter is "unhealthy", so instead of using a bit of butter on bread they bathe it in 200 gr of margarine... in case you don't know, margarine is the most unhealthy, trans-fat filled disgusting thing that has ever been made.
British supermarkets are full of "sugar-free", "diet", "light", "fat-free" processed crap. Back in Spain I don't remember a single "low-fat" yoghurt, for example. We drink mostly full-fat milk. We actually do not do diets, I have no idea what the "Atkins diet" is and have no interest in it. If we need to lose weight, we go to the nutritionist or endocrinologist, or just reduce the amount of food we eat... voilà ! You lose weight.
Whoever said Spanish people eat low carbs has never been to Spain (or maybe only to British enclaves such as Ibiza). Spanish eat EVERYTHING with bread. Spanish parents teach their kids that the bread is used to push the last bits of food onto the fork (and I am not joking!). However, we don't eat packaged sliced bread... that bread is disgusting! We eat real, loaf bread, without all the crap they put into the sliced one.
Oh, and perhaps in the touristic parts of Spain it is always hot... I come from the North-West, where it is as cold and rainy as in London (it actually snows every year in my hometown). But we still don't eat crap, nor use the cold as an excuse to gorge on cake.
French fries... don't get me going on that! Every British person I met buys the chips already half-fried and frozen. Yuck! Back in my homeland you peel and fry the potatoes in olive oil, and add some garlic, parsley and pepper to them. They are delicious! I once took my British boyfriend to a visit to Spain , my aunties coked some steak with fries to him... and he asked what those delicious potatoy thinghy-magics were! They are actually french fries, mate. What you eat at home is frozen plastic.
Weird eating habits... the UK is the country with the highest number of "-arians". Wherever you go you find vegetarians, vegans, fruitarians... even breatharians! Funny thing is, in every other country in the World, a vegetarian actually has a healthy nutrition... in the UK, vegetarians eat the same processed crap as non-vegetarians... only without animal protein. But the vegs I met would still buy pre-cooked (vegetarian) food and put it into the microwave. And they would eat vegetarian crisps, and vegetarian sausages (yuck!). Sorry, but that is not healthy at all. It is just vegetarian crap.
Obsession with "fats, carbs, proteins"... You know, the thing is, Spanish people do not count calories, do not calculate how much fat, carbs or protein goes into their food... we just use healthy foods and eat until we are not hungry anymore. We don't snack. When I was a child, not once was I offered chips, nachos or any candy between meals... why would I? I had a good meal and I was not hungry until the next one!. And we drink tap water during the day... I will never understand why British mums give Coke to their kids! Have you ever visited a Coke factory? i did once with my school... a third of the bottle is filled with sugar.
We say "no" to food when we are just not hungry... in the UK people got offended if I dared reject food! Why teach children to eat when they are not hungry?
I apologize if I sound like a smug bitch. There are lots of things wrong about Spain, and lots of good things about the Uk (well... I am sure I would find some things if I really thought about it ;). But you guys have to admit that you are not in the position to give Spaniards any lessons about food and diet.
OP, your SIL is damn right... processed cereal is a crap breakfast. And then most British people follow that crap breakfast with... a sandwich for lunch! No wonder you're starving and need "a snack" mid morning and two or three mid-afternoon! Have a proper breakfast, and eat a proper hot cooked lunch, and you will find you don't need to snack, and you will only need a light dinner, and you will go to bed on only a half-full stomach.
Oh, and you won't be fat. Humans have self-regulated their food intake without the need of a diet guru for thousands of years. You just eat natural foods.
Another bit of advice: eat socially! Don't eat on your own at home. Eating is enjoyable, and eating and talking to other people will make your meal last longer, and will make you eat slower and digest the food better. When you take longer to eat, you feel full earlier. It will also improve your social life and get you more communicative with the rest of the people, which is something that British people could learn about too.
Now, I am ready to be flamed :P
Oh, about myself, I eat what I want, including bread and chocolate, and if I get 1-2 extra kilos I just stop eating chocolate for a while, and I lose them in about a week or two. I am living in New Zealand now, and some foods are more difficult to find... but it just means I need to do 2-3 more monthly trips to farmers markets or Mediterranean food stores. If you want to eat healthy, you got to cook healthy. Forget the bloody diet foods, weight-loss pills, and ridiculous diets. If they worked, the UK would be the thinnest country in the World by now. When you are the second fattest country and the top diet-products consumers... that tells you something, doesn't it?
Right, I shut up now :P
¡Un beso!