Introducing Fat

the facts about fats and oils

Fat for fuel

Fats provide fuel for the body.  From the three macronutrients, fat provides the greatest amount of energy per kg.  This is twice as much as the same weight of carbohydrate or protein.

Fats are trending and topical because of uncertainty within the research arena but a common theme is there are healthy fats which we should all eat along with a good dose of vegetables.
Foods with a high-fat content include butter, cream, nuts, olives, avocados, seeds, eggs, cheese and obviously fatty meats, salami, sausages.


The word fat refers to both fats and oils.


What do fats do?

Fats provide energy for the body and the brain.  Eating too much fat will make you fat, but fat is an essential component of the diet.

  • Fats are valuable for transporting fat-soluble vitamins and fat-soluble anti-oxidants around the body.
  • Fats are integral to the cell structure – the cell membrane is made up primarily of fat.
  • Fats insulate body organs
  • Fats are involved in the manufacture of hormones

Fats have many functions and there are different types of fat. Fats are categorised by their chemistry and can be considered either healthy or unhealthy.

categories of fats, saturated, unsaturated
Fats are categorised based on their physical chemistry.   Saturated fats only contain single bonds in the carbon chain whereas unsaturated fats contain at least one double bond in the carbon chain.  Monounsaturated fat has one double bond, polyunsaturated fats has two or more double bonds.  Omega-3 and omega-6 are polyunsaturated, the numbers 3 and 6 indicate the placement of the first double bond in the carbon chain.

Fats have different structures

Understanding fat is about understanding the physical structure of the fat, in particular triglycerides, which are the main type of fat in the diet.

A triglyceride is three fatty acids held together by a glycerol.  Think of an “E” – the vertical part is the glycerol and the three horizontal bars are the fatty acids.  The fatty acids attached to the glycerol can be the same or different.

A fatty acid is a chain of carbons with hydrogens attached.  It is the way those carbons are holding hands which defines whether it is saturated or unsaturated.  The saturated fatty acid has a simple hand hold whereas the unsaturated fatty acid has a more intricate handhold.  It may be a mono (single) or poly (many) handholds in a ‘cis’ or a ‘trans’ grip.

The length of the fatty acid – short, medium or long chain fatty acid – determines the melting point of the fat.  A long chain fatty acid will have a lower melting point and will be liquid at room temperature e.g. oils and a short chain fatty acid will have a higher melting point and will be solid at room temperature e.g. butter. The medium chain fatty acid is in between e.g. coconut oil.


The length of the fatty acid determines whether the fat is solid of liquid at room temperature and the type of carbon bonds (handholds) determine the fats saturation.


Recommended daily intake of total fats

A total fat recommendation has not been set by New Zealand Ministry of Health as it is the type of fat consumed which is important rather than the overall fat intake but there are guidelines of between 20 – 35% of energy intake[1].  Eating insufficient fat can be detrimental to maintaining weight and it becomes very difficult to meet all nutritional requirements [1].

Using the above guidelines 20 – 35% of total energy intake for a 30 year old woman (1.6 m high) with mild physical activity requires 8800 kJ/day of energy this equates to 47 – 83 g of fat per day.

Nutrition Information Panel

Total fat content is required on the New Zealand Nutrition Information Panel per 100g of food and per serving.  Saturated fat is also required as a separate entry.

On the chocolate Nutrition Information Panel below, it has nutritional information per serving (20 g), % daily intake of the three macronutrients per serving and per 100 g of chocolate.

Nutrition Information Panel
  The fat in 20 grams (one serving) of chocolate is 5.2 grams and provides 7% of your recommended fat intake and 14% of recommended saturated fat [(3.3g * 37 kJ/g) / (8700 kJ * 10%)] intake based on a daily intake of 8700 kJ.

Summary

Food confusion is evident with fat, the science is changing and the literature is not clear on the right direction.  Fats are vital to our diet and understanding the difference between good and not so good fat is a great start.  From here, it becomes easier to focus on replacing the not so good fats with the good fats in the diet.

More resources

Behind the hype: coconut oil – Health Promotion Agency.

Behind the hype: butter – Health Promotion Agency.

Keywords: healthy food, polyunsaturated fat, monounsaturated fat, omega-3, omega-6, healthy diet, healthy fats.


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