For decades, fat was the food group supervillain, lurking tantalisingly in our cupboards and kitchens. Diets and doctors demonised it, but now science tells a very different story. We talk to health and wellness coach Sue Thomas to separate the facts from the fiction.
What kinds of fats are there?
There are trans fats, which are always cooked and used to keep things shelf-stable – they’re also usually combined with either sugar or other fats.
Then, there are saturated fats, which are solid at room temperature: so butter and the fat on meat.
And, most importantly, there are unsaturated fats like Omega 3 which are liquid at room temperature and tend to be found in fish, vegetables, nuts and seeds — these are the best quality fats.
What happens when we eat fats?
When we digest fats we produce an enzyme in our duodenum [the first section of the small intestine] called lipase that starts to break fats down.
At this point, fats don’t go through the whole digestive system, instead they basically bypass it and go into the cardiovascular system and to the liver to be processed.
This means if we’re consuming a diet that’s high in fat, all that fat is passing into the cardiovascular system. And, if it's poor quality fat in the form of trans fats, that will start to cause plaque deposits on the walls of the arteries and cause them to stiffen.
So, trans fats cause damage but others don’t?
Compared to a diet that’s full of good-quality Omega 3, there are just so many things that happen to your body when you have a diet that’s high in trans fats.
A diet full of polyunsaturated, saturated, and unsaturated fat is really important for our cellular membranes. Every cell in our body has a coating of fat which allows nutrients to pass in, and waste to pass out. Good fats make that membrane really flexible and permeable, but trans fats — because they’ve been heated to high temperatures — are damaged. They’re what's called oxidised, which makes them very stiff and impermeable. But they’re still treated by the body as a fat, and used to coat the cell.
What effect does this have?
Because it's harder to get the glucose into the cell for energy production and to move the waste out, the consequence can be that we feel quite tired, or even exhausted. And because we feel tired, we eat foods we think will give us energy — and those foods tend to be sugary, fatty foods. It’s a bigger problem that goes beyond just not having enough energy.
Good quality fats can improve energy levels, improve your immunity and keep your blood sugars and hormones balanced.
How do fats affect our hormones?
Hormones are made up of good quality fats, so if we haven't got those in our diet we’re not going to produce hormones in the right way either. Particularly for women — I believe the menopause issues in the western world have been exacerbated by the fact that for years we’ve followed low-fat diets.
The synapses in the brain are connected by fatty acids, so if you’re not eating good quality fats, they aren’t connecting properly. It’s worrying, because as a society we’re obsessed with keeping our diet low-fat and that’s the worst thing you can do. Good quality fats should be 20% of every meal.
If fats are so important, how did they get such a bad name?
In the 1960s there was a study undertaken by a professor called Ancel Keys where he fed animal fats to rabbits. They found those rabbits had plaquey buildups in their arteries and cardiovascular system and their cholesterol levels were increased. The fundamental flaw of that study is that rabbits are herbivores. They're not designed to consume those kinds of fats, but this study was blown out of proportion by the media. Consequently the diet industry jumped on it, health ‘gurus’, GPs, the pharmaceutical industry… and it was all based on a flawed research project.
The misconception remains though.
There’s no re-education around fat not being the problem, because it’s cheap to provide foods that are full of sugars and trans fats. It’s not cheap to provide good quality food that has lots of good quality fats in it.
What impact has the diet industry had on fats?
The diet industry has said for years that counting calories allows us to get our weight under control, it doesn’t focus on what we’re actually consuming. Slimming clubs all talk about a low-fat lifestyle, but if you’re consuming something low in fat it’s likely to be full of sugar.
In the western world we’ve become obsessed with calories. There are nine calories per gram of fat; compared to four calories per gram of carbohydrate. Everyone thinks ‘fats have got more calories, so if we focus on carbohydrates that will manage our weight more effectively’. But actually we’re not considering what happens in the body when we consume fat, or when we consume carbohydrate.
How do carbs and fats differ?
You get hungry when you have a spike in blood sugars and then a crash. Carbohydrates spike insulin levels, fats don’t. Fats help to balance our blood sugars and we stay fuller for longer.
Has any diet got the balance right?
I would say the Mediterranean diet is one of them because it tends to be full of naturally occurring oils and good quality fats. Olive oils, avocados and olives in their natural form — foods that slimming clubs in the western world say to avoid because they're high in calories.
Because the Mediterranean diet focuses on these, you end up eating less than if you were consuming a restricted diet focusing on calories rather than quality fats.
So, labelling something as ‘high in fat’, is counterproductive?
Some food packaging features a ‘traffic light’ system, so you could have a piece of smoked salmon in a pack and it would have a high ‘red’ fat amount, and you could then have a pie that also has a high ‘red’ fat amount — but the two things just aren’t comparable. You can’t say ‘fat is fat and whatever it is, it’s bad’. There are different types of fat and it’s really important to make that distinction.
Trans fats are bad. Saturated fats can be consumed to some extent, but not lots of them. Polyunsaturated fats, unsaturated fats – they’re really good for you. Don’t be frightened of fat: it’s a really important part of our diet — but it must be good quality.
To find out more about Sue Thomas and her health and well-being programmes, visit Sue Thomas Wellbeing.