I couldn’t have said it better myself, so here’s the intro on this subject from a Diets and Exercise blog:

“In the 1980s we were all told that to keep our heart healthy and to loose weight we need to reduce our fat intake. Everyone with a pot belly had to cut back on the bacon and fry ups to be able to avoid a heart attack and all health professionals were promoting low fat diets to keep our waist trim.
So why do we still have such large obesity rates?

Did they lie to us?

I wouldn’t go that far but I believe back then there was not enough research done to back the theory of weight loss through low-fat diet. What they assumed is that fat contains the highest calories (9kcal per gram) out of all the macro nutrients and if it is cut out of the diet it will result in the biggest fat loss by creating the highest caloric deficit.

In the 1960s and 70s, scientists established a link between high blood cholesterol levels and heart disease. And guess what? One of the most important determinants of blood cholesterol level is fat in the diet – not total fat, but specific types of fat. Some types of fat are clearly good for cholesterol levels and others are clearly bad. But instead of explaining to us what are good fats and bad fats they gave a bad name to all fats.
Time went by, people followed the advice they were given and ate their low fat diet.

Supermarkets were more than happy to jump on the band-wagon and start to produce low-fat products and offer ‘healthy cereals’ for breakfast as we said goodbye to the fry-ups.

But the number of overweight people just grew.
All the time whilst we tried our hardest to stay slim and healthy we have been doing the exact opposite.

Today adult obesity levels in the UK are soaring with 75% of the population overweight and 22% obese. Over 30,000 deaths a year are caused by obesity in England alone.”