The truth about fat

Fat is something we’re hard-wired to enjoy. Natalie Filatoff and HFG senior nutritionist Rose Carr explain what fat does to our bodies and brains.

If avoiding fatty foods is a constant struggle, don’t fret — it’s probably not entirely your fault. Scientists have found that there are a number of reasons why fat has such a hold over us.

Take evolution for starters. The presence of fat in your mouth tells your brain you have a kilojoule-rich food going down and that you’d better stock up because you never know when this big steak (or five-litre tub of ice cream or family-sized packet of chips) will come your way again. In modern times, when food is plentiful, this instinctive drive to consume fat while it’s available might play a part in the way we gain weight, but it’s not the whole picture.

Habit

We reach for fat for various reasons. You may have become conditioned to eat fatty foods by your family’s habits or by those of your social group.

Fat is one of the ingredients manufacturers can use to produce cheaper, more desirable products. Consider the fish finger or battered or crumbed fish.

“Once, you had a fish fillet. However, breadcrumbs and oil are cheaper than fish. Add them and you can sell a bigger thing for more,” says food technologist Gary Kennedy.

Fish fillets were the ultimate low-fat food, he says, “but adding fat makes them more desirable, and cheaper.”

Taste

Welcome to the palate pleasure dome, where fat equals fun. Our mouths are designed to love the feel of oil, cream, butter — in short, fat — says Damian Frank, a sensory flavour research scientist at the Commonwealth Scientific and Industrial Research Organisation (CSIRO).

He adds that, when you cook, the heat drives out the food’s moisture, helping flavours to concentrate in the fat. And when that fat breaks down in your mouth, it gradually coats your tongue, releasing those wonderful lip-smacking flavours. Conversely, if food is fat free, its flavours won’t last as long in your mouth.

Fat also enhances the textural variety of foods, making potato chips crisp and giving chocolate its satisfying solidity. “We love the sensation of food changing from one pleasant consistency to another in our mouth,” says Frank. When chips seem to dissolve on your tongue, or chocolate melts in your mouth, it’s a gratifying sensory, often sensual, experience.

Stress

Research shows that eating fatty foods can counteract the stress response in animals.

Professor Margaret Morris, a psychopharmacologist at the University of New South Wales, has found that foods rich in both fat and sugar can lower feelings of stress in animals, perhaps because eating such foods stimulates the brain to release feel-good hormones dopamine and serotonin. These hormones positively influence mood in people, just as they do in animals.

We do need fat

It’s important to recognise that we need fats in our diet. Our cells require a variety of different fats to maintain cell walls, among other cellular processes. Fats provide essential fatty acids required to make hormones and the fat-soluble vitamins A,D,E and K. The beta-carotene in tomatoes, for example, is more readily absorbed when tomatoes are cooked in a little olive oil.

In short, we are naturally predisposed to seek some fat in our meals so if we don’t get it, this inclination may contribute to our feeling unsatisfied and wanting to eat more or to eat and snack more often to feel full.

Beware the fat with sugar combo

Problems arise when we eat things that fat tends to be packaged up with these days.

In 2005, a Swedish study found that fatty, sugary foods can override our normal appetite regulation. In fact, these super-sweet and fatty foods not only ramp up our hunger signals but also increase the amount we need to eat to feel satisfied.

On top of that, the dopamine release that makes us feel good may also drive us to return to fatty, sugary foods again and again.

Fat plus salt is twice as tempting

If fat is a flavour vehicle, then salt is a flavour enhancer. This dynamic duo packs a double-whammy. Both salt and fat have ‘desensitising’ effects. The more you eat, the more you become dulled to the flavours, and the more you need to get that pleasing taste.

So by eating these foods regularly, you can easily end up on a treadmill of heart-risky, salty, fat-laden and very high kilojoule foods.

Fat sensitivity

Some people are more sensitive to the taste of fat than others, according to new research from the Food Sensory Science Department at Deakin University in Australia.

As Associate Professor Russell Keast explains: “If you’re less sensitive to fatty acids, you don’t feel full when you eat fat, so you’re likely to eat more of it, or more of something else, to satisfy your hunger.”

So when people who are not sensitive to fat start eating a slice of bacon or a doughnut, for example, they’re likely to keep eating because their body doesn’t tell them to stop. And these people are more likely to be overweight, as Keast’s research confirms that the taste buds of overweight and obese people are less sensitive to fat in foods.

Here’s the important thing: Keast’s research also indicates that eating less fat actually increases your sensitivity to it. And with increased sensitivity comes better self-control.

His team placed people who were insensitive to fat, and who had become overweight or obese, on a low-fat diet for four weeks. He found they developed a significantly increased ability to identify low concentrations of fat.

This suggests that over time, you can train yourself to find that you are satisfied with eating less fatty foods.

Why fat is not all bad (or all good): the saturated fat debate

Recent media reports have suggested that saturated fats — the type found in meat and dairy, among other things — may not be as bad as was previously thought. This adds to a popular theory that saturated fats might actually, in fact, be good for us. So should we be loading up on cream and butter instead of olive oil and low-fat dairy?

As is often the case in science, the answer is not simple. Saturated fats include more than one type of fat — they are a category of fats. And as is the case with polyunsaturated fats — where an overload of omega-6 in relation to omega-3 is thought to be unhealthy — some types of saturated fats seem to be less harmful than others.

Current evidence suggests that palmitic and myristic acids — saturated fats found in butter, cheese, milk, palm oil, coconut oil and meat — are potentially harmful, contributing to inflammation, elevated lipids and vascular disease. On the other hand, stearic acid — also found in meats and dairy products, as well as dark chocolate — appears not to be harmful. The scientific jury is still out on lauric acid, the main saturated fat in coconut fat. (We may find this is also benign but right now our advice is to use other fats over coconut fat.) So lumping all saturated fats together may now be adding to the confusion. But it doesn’t follow that more saturated fats are therefore good for us.

It is worth noting there is a lot of evidence that a diet low in saturated fats but high in plant food and including healthy unsaturated fats from fish, nuts, seeds and olive oil is good for us — the Mediterranean diet has been shown to be one of the healthiest diets in the world. With important modifications on the common western diet, this eating pattern is not completely different to what we know, making it both attainable and sustainable in the long term.

A lot depends on what else we’re eating, too. A diet high in saturated fats that is also high in sugary foods and refined carbohydrates and low in vegetables (as is the case for a lot of people in the Western world) would not promote good health for anyone. On the other hand, if we’re eating lots of plant foods and no junk food, cakes or biscuits or sugary drinks, then a little bit of butter is unlikely to hurt us. As always, we need to remember to stand back and look at the big picture, which includes our diet as well as other lifestyle choices.

Are low-carb, high-fat diets the way to go?

A popular theory currently being promoted is that a diet that’s up to 80 per cent of energy from fat, including saturated fat, and extremely low in carbohydrate (about ten per cent of energy) could be the key to weight-loss. While this is an interesting theory, it’s important to note it is just a theory at this stage. Research is underway into whether or not this could be a useful approach for weight loss, but in the meantime health experts warn that we just don’t know whether there is long-term benefit — or harm — in these kinds of diets. While it’s good to see a focus on whole, unprocessed foods, and we’ll be following the research with interest, right now we recommend a moderate approach rather than extreme diets.

How to eat fat wisely

We do need fat in our diets. It plays lots of important roles in our bodies. On average our fat intakes in New Zealand are at 34 per cent of energy, and up to 35 per cent of energy is recommended. So it’s not that most of us consume too much fat overall but it’s worth looking at the types of fat we’re having. It’s recommended we get less than 10 per cent of energy from saturated fats but on average, we get around 13 per cent (nearly one-third higher).

Here are some tips for getting the best from the fat you eat:

• Limit or avoid baked and fried foods such as cakes, muffins, pastries and deep-fried takeaways, which combine saturated fats with refined carbohydrates and sugar, and often contain harmful trans fats, too. 
• Enjoy healthy fats from plant foods such as nuts, seeds, avocado and olives to increase your antioxidants and mimic the Mediterranean diet. 
• Include oily fish in your diet regularly to boost your omega-3. 
• Choose leaner meat or trim most of the fat from your meat to cut saturated fats. 
• Avoid processed meat. 
• Choose mostly low-fat dairy products. 
• If you choose to eat butter, cream, chocolate or coconut fat, keep servings small and savour them for their taste and texture. 
• Think of the big picture: eat lots of colourful vegetables and fruit, cut back on refined and processed foods and sugary treats and limit alcohol. Then you’ll have room for healthy fats.