The Longevity List by Professor Merlin Thomas published by Exisle Pu">
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Do I really have to eat less fat

By: An extract from the The Longevity List by Professor Merlin Thomas

Do I really have to eat less fat?
The following article is taken from a chapter of the book The Longevity List
by Professor Merlin Thomas published by Exisle Publishing

Q: Is fat really a problem?
A: Look at your waistline and decide.

Q: How much fat should I be having?
A: Less.

Q: Why is burning fat a bad idea?
A: Ever heard of tear gas?

Q: What about taking fish-oil supplements?
A: Fish oil only works in fresh fish (otherwise it smells fishy).

Q: Should I care about trans-fats?
A: You mean the poison disguised as fat?

Q: Is margarine better than butter?
A: They are both over 80 per cent fat.

Some people think that it's not how much fat we are eating that is the problem, but rather the kinds of fat and their unnatural proportions.
To understand how the fats in our diet potentially work for or against us, it is necessary to talk about their chemistry. Fortunately, it's really not that complicated.
Just imagine three long chains all linked to a single short backbone, something like a cricket wicket or the letter 'E'. Each stump is called a fatty acid. The three long stumps are linked to one another by a special sugar (called glycerol), which looks like the bails on the top of the wicket. The whole complex is called a triglyceride.
Triglycerides are the main energy store in all animals. Plants also store triglycerides inside their seeds, nuts, corn and other grains. Some plants also add triglycerides in the fleshy pulp around their seeds (e.g. olives, avocado and palm seeds). Altogether, over 95 per cent of the fat we eat is in the form of triglycerides.
All the triglycerides we eat can be used as fuel in our body. But they are not all the same. The length of their fatty acid stump/chains, as well as the presence of double links between adjacent carbons in the chain, changes their physical properties. When double bonds are present in a fatty acid chain, these are called unsaturated fats.
Fatty acids without double bonds are said to be saturated. All natural products have a balance of saturated and unsaturated fats.
The reason a double bond or two makes a real difference is because it introduces a slight kink into the structure. This is like a pack of cards when some of the cards have been folded or bent - they just don't stack neatly together the way they did when they were all crisp and flat. In much the same way, without any kinks in their structure, straight saturated fat makes a great way to pack lots of fat into a small space.
This is one reason dieticians go on so much about how much saturated fat we include in our diets. For the same volume, denser saturated fat brings in more calories. For example, spreading our toast with butter, which is rich in saturated fat, adds more calories than the same volume of polyunsaturated margarine, even though both are over 80 per cent fat.
About 40 per cent of the triglycerides languishing in our body fat are saturated fat. This is also true for most animals. So when we eat animal fat in beef, pork, chicken, a burger or a sausage, about 40 per cent of the fat we are eating is going to be saturated fat.
Dairy products like cheese, milk and ice-cream have even more fat and about 60 per cent of it is saturated fat. Low-fat milk has half as much fat as full-cream milk, but 60 per cent of what it has is still saturated fat. Skim milk (made when all the cream is removed) has about ten times less fat than low-fat milk. Consequently, cream has ten times more fat than low-fat milk.
Adding together all the meat and all the dairy we eat constitutes about half of all the saturated fat we normally eat. Lacto-vegetarians cut all of these out and so usually eat half as much saturated fat as everyone else. But they still eat saturated fat. This is because saturated fat is also contained in many of our staple foods made from cereal grains (e.g. bread, pasta, cake, breakfast cereals, etc.), as well as vegetable oils and spreads. Although these products contain much lower proportions of saturated fats than unsaturated fats, given our high intake of them it all adds up in our diet.
The dense packing of saturated fats is also how fatty things like butter, lard, tallow and cocoa butter can stay solid at room temperature. Even coconut oil will start so solidify if the temperature drops below 24oC (76oF). When heated, saturated fats are still able to melt. This is very useful on toast. But it is also widely used in cooking to give us that pleasing melt-in-the-mouth sensation, as in chocolate or pastry.

All the kinks in unsaturated fats mean that when they are purified they are generally liquid (an oil) at room temperature, like most vegetable, corn and seed oils.

Some fats have many double bonds in their chains. These are called polyunsaturated fatty acids. Some have only one kink in their chain. These are called monounsaturated fatty acids.
Having only one kink makes monounsaturated fats more flexible than solid straight saturated fats. Consequently, monounsaturated fats are found in all animals and plants where they provide extra flexibility to membranes while being oily enough to keep the water out. Around 55 per cent of the fat stored as triglycerides in our body is monounsaturated (chiefly oleic acid). Similarly, the major fat in the beef, pork, chicken breast and egg yolk we eat is also monounsaturated fat. About one-third of the fat in dairy products is also monounsaturated. Consequently, all the things that provide saturated fat to our diet are also the major sources of monounsaturated fat too.
The one kink of monounsaturated fats also confers the useful culinary property of being liquid at room temperature but still having the capacity to become solid when refrigerated. This means that oils naturally rich in monounsaturated fat, like peanut, avocado and canola oils, don't take kindly to the freezing cold.
The polyunsaturated fats have so many double-bond kinks in their structure that we usually call them oils rather than fat.
Polyunsaturated oils with their multiple kinks such as corn, soybean, cottonseed, linseed (flaxseed) and safflower oils, can stay oily well below the freezing temperature of water. This is one of the reasons they are found in such high amounts in krill and cold-water oily fish (but more on fish oil later in this chapter).
Today about 20 per cent of the fat we consume is polyunsaturated, over half of which comes from seed and vegetable oils used in cooking and another quarter from the wheat and other cereal grains in our diet. Interestingly, less than 3 per cent of our body fat is made of the kinky polyunsaturated variety. This is not because we don't use it. As detailed below, there are actually many things we use it for. It's just that the extra kinks in polyunsaturated oils do not lend themselves to efficient mass-storage in humans.
By contrast, plants usually store triglycerides in a polyunsaturated form. Some have a larger component of monounsaturated fat (e.g. olives, peanuts and rapeseed). Occasionally, special plants (e.g. coconut, cacao) use saturated fat for storage. This is why different vegetable oils can have very different properties, both in the pan and in the pantry.

The same double bonds that make unsaturated fats oily are also their Achilles heel, because they make them uniquely vulnerable to attack by oxygen, especially when they are heated. In other words, those double bonds mean that unsaturated fats like vegetable oil can go off (or spoil). This is the main reason that humans have historically preferred using saturated fats from butter, lard and tallow (i.e. fat from animals).
Saturated fats do not have double bonds and don't go off as easily, so can be stored for long periods or left in the pantry at room temperature without smelling out the place. Of course, copious preservatives are added today to polyunsaturated fats to achieve a longer shelf life. So going off is not an issue for modern polyunsaturated oils and spreads made from them, like margarine. But preserving unsaturated fat is tricky or impossible for whole foods, like fish. For example, a fish can get pretty smelly if it is left out of the water for a prolonged period of time. This is mostly because of the spoiling of the polyunsaturated fats in fish oils. And this is also why fish must be stored carefully on ice or in the fridge and used as soon as possible. Even then, fish starts to smell bad long before it is actually rotten.
Having only one double bond makes oils rich in monounsaturated fats (e.g. olive oil) more resistant to going off in the pantry or needing as many preservatives in the bottle compared to polyunsaturated oils. This makes cooking with monounsaturated fats historically very popular in the kitchen, especially in Mediterranean cuisine.
Double bonds also make a difference to the toxic fumes that rise from the pan when we cook with them. The best known are aldehydes, which form as fatty acids and are blown apart under heat.
The hotter it gets the more they form, so toxic fumes are greatest while deep-frying or pan-frying, although we can still get some while stir-frying. Cooking oils with lots of double bonds generally produce more aldehydes and other toxic species than those with few or no double bonds. But regardless of what we use, if we heat it enough, some smoke will get in our eyes.

Smoke point blank
When oil is heated hotter and hotter, at some point (known as the smoke point) it will vaporize, releasing a bluish smoke as it rises. This urgent smoke signal means that the oil is far too hot for cooking. You need to immediately take it off the burner otherwise your kitchen and your house will fill with toxic smoke particles and the pungent smell of burnt fat.
That (all-too-familiar) fast-food restaurant smell comes from burning of glycerol (the bails on top of the three fatty acid stumps in the triglyceride cricket-wicket analogy, remember?). Consequently, toxic smoke can rise from any cooking oil whether it is predominantly saturated, monounsaturated or polyunsaturated.
However, saturated fat burns a little faster in the pan (i.e. smokes at a lower temperature) than polyunsaturated oils. This is because, without double bonds, the heat (energy) has nowhere to go. Consequently, we generally have to use more saturated fats (e.g. lard, coconut oil) when cooking over high heat than polyunsaturated oils, or the frying pan dries out.
Other things mixed in with the oil can also lower the smoke point. For example, the less-processed, extra-virgin olive oil has a smoke point 100 degrees lower than light (highly refined) olive oil which has had the colour, flavanols and other elements that can easily catch fire removed. This is also why clarified butter (known as ghee) works and is so popular in cooking, as it has had its milk proteins (which readily go up in smoke) removed, thus raising the smoke point by 50 degrees.
Being pure and saturated are not the only things that make oil smoke. Re-using the same cooking oil again and again progressively lowers the smoke point by freeing up the fatty acids and glycerol from the triglyceride-complex, and so aiding their escape. This is partly why those old chip shops (well known for re-using their oil) were so smelly.

Big fat Greek
Whether it is saturated, mono- or polyunsaturated, fat provides energy for our metabolism. All fat will make us fatter if we eat too much of it relative to our level of physical activity. So whether one kind of fat or another is a dietary hero or villain ultimately comes down to whether it has any other effects beyond its impact on calorie balance.
One of the reasons we have been told for so many years that it's not how much fat we eat but the kind of fat we are eating that's the problem is the so-called 'Mediterranean paradox'.
The story goes that in the 1950s, when things were going so wrong in the United States in terms of heart disease and diabetes,
Mediterranean countries like Greece and Italy were experiencing record low rates. This made no sense, because their diet contained large amounts of fat, and fat was supposed to be bad for you. Ignoring the fact that the Mediterranean had been decimated by war a decade earlier (so people were not so well off and were living off the land rather than mass-production), the idea emerged that perhaps there was something special about the Mediterranean diet that conveyed a protective effect. But the critical ingredient(s) behind this rough magic remained to be established.
A classic Mediterranean diet is a pattern of eating lots of unprocessed cereals, vegetables, legumes, fruits, nuts, fish and olive oil with reduced amounts of meat, milk and milk products and sugar.
Wine, as a rule, is taken with meals and in moderation. Essentially this all adds up to a high ratio of calories from (whole) plants compared to calories from animal products or highly processed foods.
But of all the many different ingredients in the Mediterranean diet, the finger was pointed at the large amounts of monounsaturated fat they ate compared to the supposedly heart-stopping saturated fat that dominated in other countries. While Americans used butter, lard and shortening, Mediterranean cooking had olive oil at its very heart.

The logical explanation given for the Mediterranean paradox was that while saturated fat was driving up cholesterol levels in America, the
Greeks' preference for olive oil and only a moderate intake of animal fat meant that they had much lower cholesterol levels and therefore fewer heart problems.
It is perfectly true that diets rich in saturated fat have a greater effect on our blood cholesterol levels than unsaturated fat. And if there are any benefits from cutting out foods that are high in saturated fat (e.g. butter) or switching to foods that are lower in saturated fat (e.g. margarine, olive oil), they are almost entirely due to lowering the levels of bad cholesterol in our blood.
Because of the link between cholesterol and saturated fat, and the link between cholesterol and heart attacks, saturated fat has been unequivocally vilified in the latter half of the 20th century. So effective has this campaign been, with even doctors advising their patients to eat margarine, that modern generations now eat less than half the saturated fat of fifty years ago.
But while cutting out saturated fat was the only way to lower bad cholesterol in the seventies, its effect was only modest at best. Today we have many much better ways to achieve this.
Moreover, the ultimate cost to our health of eating more unsaturated fat may not have been worth it.

During the latter half of the 20th century, the amount of fat in the average diet changed radically. We were not eating much less fat as a proportion of our diet. Rather, based on the Mediterranean paradox and the supposed explanation for it, people started to replace saturated fat with polyunsaturated substitutes (e.g. replacing butter and lard with margarine and vegetable oil). Today, only a third of the fat in our diet is saturated. The great majority of the remainder is monounsaturated fat with some polyunsaturated fat on the side making up 8 to 10 per cent of the total fat we eat.

The problem with this shift is that the fat in our diet is far more than just a danger to our cholesterol levels or our waistlines. It also has a range of vital functions in the human body, from maintaining our immune system and brain function, to regulating blood flow and protecting against injury.
Some polyunsaturated fats are positively essential for our health.
In fact, they were once known as vitamin F and must be obtained from the food we eat, just like all the other vitamins. This is because, while our body is able to generate and store all other kinds of fat, we can't make the useful ones that have reactive double bonds, specially placed exactly three or six links from the end of a fatty acid chain.
Omega is the 24th and last letter of the Greek alphabet, so the end of a fatty acid chain is called the omega. These essential fats are usually called the omega-3 (ω-3) and omega-6 (ω-6) fatty acids. Their unique chemistry makes these fats very useful for creating other things, including essential regulatory and signalling chemicals.
Although humans can't make these special fats, plants have no trouble at all. Similarly fish and animal fat can also contain useful amounts of these essential fats (because they eat mostly or entirely plants).
But the fact that we can't get by without them doesn't mean that they are essentially good for us in the very large doses and the unnatural ratios we often take them.
Omega-3 fats and omega−6 fats look pretty similar to each other (they just have one double bond in a different place), so they compete for many of the same chemical reaction pathways in our body. However, the products of the reactions that occur when using omega−3 fats are very different, chemically and functionally, than those that occur when using omega−6. So the net result of what happens when we eat polyunsaturated fat also depends partly on how much omega-3 is present versus omega-6.
It is thought that a one-to-one ratio of omega−3 to omega−6 (or as close as possible) is optimal for good health. But in a typical modern diet, for each omega−3 fat we consume there are at least a dozen omega−6 fats, and very often much more than this. Undoubtedly, this imbalance can alter the balance of signalling chemicals being made, and potentially have consequences on our health, including depression, heart attacks, stroke, arthritis, osteoporosis, inflammation and some forms of cancer.
To address this imbalance, it is now widely recommended for our health that we increase our intake of omega−3 fats. The most common sources of omega−3 fats in our diet are the plants we eat, as well as any fat from the animals that eat them. Egg yolks are mostly saturated fat, but the amount of omega-3 they contain can be enhanced by feeding chickens with omega-3-rich plants (e.g. linseed/ flaxseed, santolina) or sometimes fish-oil. This is because omega-3 polyunsaturated fats are especially high in cold-water oily fish and in the oil that is extracted from them. This why most guidelines recommend that we should eat them more often than we do and many people take fish-oil supplements in their stead.
As well as raising our intake of omega−3 through fish-oil and the like, another recommended way to bring the omegas back into healthy balance is to lower our intake of omega−6 fats. This is one of the key aims of the Paleo diet, which reduces the intake of grains, seeds and their oils (i.e. most of the polyunsaturated omega-6 in our normal diet), replacing them with monounsaturated fat-dominant oils (like olive oil) and saturated fats like butter. Used in this way (and in modest amounts) the reformed villain - saturated fat - is made to work for us instead of against us.

In the seventies and eighties, avoiding saturated (animal) fat at all costs was the central tenet of a healthy diet. Out went butter, lard, tallow, palm and coconut oils. This created an opening for a new kind of fat to enter our bodies called trans-fat. Although hailed as the saviour, in the end it turned out to easily be the most maleficent fat of all.
Trans-fats are typically created when unsaturated fats (usually from vegetable oils) are overheated. This may be deliberate, for example, to make solid shortening (e.g. Crisco) or ghee from liquid vegetable oil. For example, some Vanaspati (vegetable ghee) products sold in India may be over 20 per cent trans-fat.
Sometimes trans-fats are created accidentally, for example, when products that come out of the frypan carry the stain of trans-fats generated in the overheated, reused vegetable oil in which they have been fried.
The discovery of how to make trans-fats was so revolutionary that its inventors received the Nobel Prize in 1912.
Trans-fats are a deceptively clever piece of work. Instead of double bonds creating a nice kink in its structure like other unsaturated fats, trans-fat gets twisted around, which paradoxically results in a super straightening and stiffening of its carbon backbone.
This upright chemical structure means trans-fat looks and behaves like a saturated fat when it comes to cooking. It could pack in tightly and be semi-solid at room temperature, just like butter. It could equally have melt-in-the-mouth texture on heating and provide a palatable alternative to other fats in making baked goods. In fact, head to head, trans-fat more reliably produces uniformly fluffy pastries than butter.
Being tricky, trans-fat also has a longer shelf life, and is less prone to going off (spoiling) than polyunsaturated fat found in conventional vegetable oils. Trans-fat also doesn't burn as easily as saturated fat, so there is less fire and smoke at fast-food outlets. It is also cheaper to mass-produce than butter.
All this culinary chemistry without the price tag. With trans-fats on board, products could now be considered healthy (and became popular) because they did not contain the nutritional devil, saturated fat, and its deleterious effects on our cholesterol levels. No wonder we all switched our butter to margarine and vegetable oils in the seventies.
It turns out there really was a (hidden) catch. The same super-resistant chemistry that made trans-fat a culinary wonder also made it deadly for our health. In fact, pound for pound trans-fats increase the risk of dying prematurely more than any other component of our diet. There appears to be no safe limit for trans-fats. Even a small intake may be sufficient to begin increasing the risks for death and disease.
Recognizing this, most of the previously common sources of trans-fats, like margarine and vegetable shortening, have had their shot at redemption. Today most of them contain less than 0.2 per ent trans-fat. However, some processed foods and spreads still contain trans-fats. The chief offenders include microwave popcorn, certain biscuits, cakes, potato crisps and savoury pastries. Sometimes the trans-fats are listed on their nutritional labels. If they aren't listed then it's a fair bet the producers don't really care about your health.
It is likely that mandatory testing and listing of trans-fat content will soon be required in many countries.
All the reputable mega-chain takeaway and fast-food restaurants have also switched their oils to canola oil free of trans-fats. While this makes them less unhealthy it still does not make them healthy.
Deep-fried foods from unscrupulous operators still run the risk of generating trans-fats, especially those reusing vegetable oils to reduce costs. Again, it is likely that regulations will eventually catch up with them, as there have been calls for banning all trans-fats from restaurants and fast-food outlets. In some places they are already outlawed. However, in many developing counties, trans-fats remain a major concern, especially in India and South Asia, where vegetable ghee and deep-frying are culinary icons and staples for cooking at home.
Finally, some trans-fats do occur naturally in meat (fat) and in dairy products like cheese and butter. But these are not the synthetic ones that caused so many problems for margarine and are chemically different again, containing both trans-fat and unsaturated fat elements. These natural trans-fats are not thought to be a major problem to human health.

The bottom line
It's a topsy-turvey world. Saturated fat was bad and now it's not.
Trans-fat and polyunsaturated fat were the solution, but now they are the problem. Fish oil saved the Eskimo, but now it just smells fishy.
Reducing our dependence on a low-fat diet was essential, but now we are eating too many sugars/carbs.
Paul Newman once said from the inside of his racing car that it was useless to put on the brakes when the world was upside down.
This is exactly how many people feel about their diet. If you're crashing anyway and nothing makes sense, why slow down? And what good would putting on brakes do, anyway?
But we are not there yet. We still have plenty of time to turn the wheel and slow down. And targeting the fat we are eating can make a big difference.
The fat we eat is not intrinsically bad or good, only made so by how we use it. Obviously, eating too much fat readily adds to our calorie count and ultimately to the pantry around our waist. So cutting out unnecessary fat is one simple way to cut calories as well.
Most of the saturated fat in our diet comes from meat and dairy.
So if we can only make a habit of eating the lean meat or substituting an amount of something else that doesn't have the fat (like legumes for mince) we lose nothing except for calories.
Most of the unsaturated fat in our diet (as well as a quarter of the saturated fat) comes from oils and spreads, which together contribute as many calories to our waistlines as all the saturated fat we currently eat. It is possible to cook without oil or at the very least with less oil. Today we have non-stick cookware, a zillion herbs and spices, steamers, slow-cookers, an abundance of whole unprocessed foods and a host of other opportunities to ditch the oil. This means fewer calories, not less food. It also means less tear gas.

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