Friday, 1 February 2013

Fats: the good, the bad and the ugly

Let’s face, fat has had a lot of bad press. We associated it with obesity and heart disease, and reducing fat in the diet has long been the standard advice for improving health. But does fat really deserve all of the blame that is attributed to it?

Not all fats are created equal - some are good, some bad and others, quite frankly, ugly. In terms of energy content, fat is fat. At 9 kcal per gram, it doesn't matter whether you eat butter, lard or olive oil - they all contain the same amount of calories. But energy content aside, the different fats have variable qualities and variable effects on the body - some are good for you, others not so good. 

Fat plays several essential roles in the body, from insulating us against the cold to regulating our hormone levels, we simply can’t maintain a healthy, functional body without fat. Fat is an essential fuel source for the working body, and whether you’re a first class athlete or sat on your bum all day, this is a simple fact – your body NEEDS fat.

But not too much. 

Balance and moderation, as always, are key. There are dangers associated both with having too much, or too little fat.

Too much fat:

  • High fat diets are associated with excess body weight, an increased risk of cardiovascular disease, stroke and several cancers.
  • An excess intake of fat can displace other nutrients – if we eat a high fat diet, we may find that our intake of carbohydrates and/or proteins drops. 
  • When carbohydrate intake falls, our stores of glycogen are compromised. For athletes this can have serious consequences on training and competition. 
  • Triglycerides (the smaller units that make up fats) are stored in the muscles, and are an important fuel source for sporting performance.

Too little fat:

  • Fat is a good source of energy (9 kcal per gram), and a low intake can result in inadequate energy consumption. Fats are an important source of vitamins K, A, D and E. Eating a low fat diet can limit our intake of these essential nutrients.
  • Low fat intake reduces the storage of triglycerides in the muscles, and so compromises this important fuel source.
  • Fat is important in regulating several hormones, and a low fat diet can result in an altered menstrual cycle and can also effect fertility.

Current recommendations

<35% of total energy should come from fat.

For a 2000 kcal diet, this is 700 kcal/ 78g of fat

For a 2500 kcal diet, this is 875 kcal/ 97g of fat.
Saturated and trans fats should be kept to a minimum.

The good...

Some fats are essential - the clue is in the name: Essential Fatty Acids (EFAs). These cannot be synthesised in the body, so it's vital that they are eaten as part of the diet. EFAs are found in unsaturated fats - a family of fats that can be split further into mono- and polyunsaturated fatty acids (MUFAs and PUFAs). Both have the potential to lower 'bad' LDL (low density lipoprotein) cholesterol, whilst also raising levels of 'good' HDL (high density lipoprotein) cholesterol. 

MUFAs are found in oily fish, olive oil and spreads based on olive oil, nuts (including almonds, cashews, peanuts, pecans and pine nuts), sesame seeds and tahini, and avocados. 

PUFAs (which include Omega-3 and -6 EFAs) are found in oily fish (including salmon, mackerel, and sardines), oils based on vegetables and seeds (vegetable, sunflower, sesame and soy bean oil), and nuts and seeds. 

The bad...

Saturated fats are commonly referred to as 'bad fats'. They are solid at room temperature and found in animal products, including meat, milk (full fat), cheese and butter, as well as products that include these as ingredients. Saturated fats can also be found in some vegetable-based products, including coconut oil/milk/cream and palm oil. 

A high intake of saturated fats increases levels of LDL cholesterol in the blood, and is linked with increased risk of cardiovascular disease. 

The ugly... 

Trans and hydrogenated fats have a double whammy of effect, increasing both total and LDL cholesterol and lowering the good HDL cholesterol, thereby putting you at greater risk of heart disease. 

Some trans fats occur naturally in foods in very small amounts, and these include red meats (beef, lamb, veal) and in full fat dairy products. Most trans fats are found in artificial sources, such as those used in the manufacture of cakes, biscuits, pastries, and pies. 

Trans fats have no known benefit to health, and should ideally be avoided.

But eating fat makes you fat, doesn't it?”

Actually, no. It is an excess of total energy that leads to weight gain – eating more than you use. In terms of weight gain, it doesn’t matter where these calories come from – fat, vegetables, carbs, protein… if it’s more energy than you need or use, your weight will increase.The main reason that people associate fat with weight gain is that fat is energy dense – it contains 9 kcal per gram, the highest energy content of the macronutrients (carbohydrates, proteins and fats). So it can be easy to over consume calories without an obvious increase in the amount of food you’re eating. It's hard to deny that it can play a role in gaining weight, but if accounted for within a healthy, balanced diet, there’s no reason to blame weight gain purely on eating fat.

So what's the take home message?

Enjoy the fat that you include in your diet!

•       It can taste nice – who doesn’t like a piece of hot buttered toast?
•       It’s enjoyable – see above! Hot buttered toast!
•       It adds variety to the diet – avoiding all sources of fat severely reduces our options when   
        choosing what we eat.
•       Fat contains essential vitamins and is a good source of energy.


•       Moderation is key – stick to the guidelines on how much fat you eat, and account for it in 
        your daily intake to avoid weight gain.
•       If you’re trying to lose weight, reducing high fat foods can save you lots of calories.

•       Avoid saturated, trans and hydrogenated fats – they don’t confer any health benefits and 
        increase your risk of cardiovascular disease, stroke and several cancers

So that’s it. Fat shouldn’t be the pariah of the nutrient world – it can be good, it can be bad. But much of that depends on you and what you do with it…

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