Category: Weight Loss

This is a continuation of my post regarding fats, see part 1 here.

What are omega-3 and omega-6?

Omega-3 and omega-6 are essential fatty acids found in polyunsaturated fats. They are essential because they cannot be made by the body and are required for good health, so it’s important that we get these fatty acids from our diet.

Omega-3, or alpha-linolenic acid, can be found in rapeseed oil, dark green leafy vegetables, walnuts and seeds. Some eggs are also fortified with omega-3. Oily fish (salmon, mackerel, sardines and herring) are a rich source of a specific type of omega-3 that can help reduce inflammatory responses and blood clotting, thereby reducing risk of heart disease. Current recommendations state 1-2 portions of oily fish per week. Omega-6, or linoleic acid, is found in vegetable and nut oils such as sunflower and peanut oil.

There is growing evidence to suggest that omega-3 and omega-6 can help lower our risk of heart disease and some studies show reduced risk of type-2 diabetes and Alzheimer’s disease.

Coconut oil; good or bad?

There have been a lot of health claims about coconut oil recently, but is it all it’s cracked up to be?

Firstly, it should be noted that coconut oil is around 92% saturated fat. As you can see in the graph below, this is extraordinarily high and, using the general ‘rules’ regarding saturated fats coconut oil should be avoided. However, the composition of coconut oil is unusual. A large proportion of the fats found in coconut oil are medium chain fatty acids.

…What are medium chain fatty acids?

Fatty acids are the bits attached to the glycerol backbone (go back to the structure of a triglyceride explained in part 1). Short, medium and long are terms used to indicate the length, or number, of carbons present in the fatty acid chain. Short (0-6 carbons) and medium chain (6-13 carbons) fatty acids are digested, transported and metabolised more quickly than long chain fatty acids (14+ carbons). This could mean that the high concentration of medium chain fatty acids found in coconut oil results in it behaving differently within the body to most saturated fats.

It may also be that the length of the carbon chain changes the impact the fat has on blood cholesterol levels. For example, research suggests that long chain fatty acids increase total and LDL (‘bad’) cholesterol while medium chain fatty acids increase the HDL (‘good’) cholesterol and have a neutral effect on LDL. However, more research is needed to confirm this.

What about the other health claims of coconut oil?

About 49% of the medium chain fatty acids found in coconut oil is lauric acid. It has been suggested that lauric acid has special antibacterial properties. However, many of the health claims that exist around coconut oil and it’s antimicrobial properties are not yet proven. There are also claims suggesting coconut oil increases metabolism therefore aiding weight loss. Unfortunately, very few studies investigate health benefits of coconut oil, especially when compared to the substantial evidence backing health benefits of mono and polyunsaturates (see part 1). Plus, it is consumed in such low quantities that any impact on microbes or metabolism is likely to be minimal.

Having said this, coconut oil is fine to use in small amounts or as a replacement to other oils in cooking. It can add a tasty nutty flavour to food and the presence of medium chain fatty acids may have a beneficial effect on blood cholesterol. Coconut oil, in particular, is a fat that requires lots more research!

So what fat should I choose?

There are lots of different types of oils and spreads available, and people may use different types for different things.

The biggest difference between butter and different types of spread is the saturated fat content. The graph below demonstrates the amounts of fat present in different types of spreads. (Values have been averaged from commonly used brands but can vary).

Which oil and spread you choose is likely to depend on lots of things; taste preference, health benefits, cost, habit etc.

In summary, to choose a fat low in saturates with higher proportions of mono and polyunsaturates is best for heart health, i.e rapeseed/olive oils and spreads. However, if used sparingly (as any fat should be anyway!), fats with higher amounts of saturates (such as butter and coconut oil) can be incorporated as part of a balanced, healthy diet.

It’s important to remember that all oils and spreads are fats, so whatever ones you use should be in small amounts, especially if you’re trying to lose weight.

At times, it seems like the media change their mind on a daily basis about whether fat is good or bad, which ones are better and which ones to avoid. So, to clear it up, I’m going to start at the beginning…

What is a fat?

In chemistry, fats are called lipids. There are three main types of lipids; triglycerides, phospholipids and sterols. Most of the fat we eat is in the form of triglycerides, so for this blog post I’ll be looking specifically at these.

Triglycerides are made up of 4 components; a glycerol backbone and 3 fatty acid chains. They look a bit like this;

OR

The fatty acid chains can be saturated or unsaturated, this describes how the molecules in the fatty acid are joined together. Saturated fats have no double bonds, unsaturated fats have at least one double bond (as seen in the bottom fatty acid chain above). Generally speaking, saturated fats tend to be solid at room temperature and are from animal sources. Unsaturated fats are liquid at room temperature and tend to come from vegetable or plant sources.

Why do we need fats?

Fat provides energy; around 9 kilocalories (kcals) per gram. It’s important that we have some fat in our diet because it’s needed to transport and aid absorption of fat soluble vitamins. Fat also provides vitamins A, D and essential fatty acids that cannot be made by the body. However, too much fat can lead to weight gain and put us at risk of health problems in later life.

What are the different types of fat?

There are three main types of fats; saturated, monounsaturated and polyunsaturated. Most foods contain a mixture of all of these, but usually one type of fat is present in larger quantities than the others. There are also trans-fats, these are a specific type of unsaturated fatty acid. Trans-fats are found in low levels in some foods but are also formed in food manufacturing.

Saturated and trans-fats are less healthy, because they bring about an increase in overall blood cholesterol levels. Foods high in saturates include; fatty cuts of meat, butter, cream, cheese and pastries. Trans-fats are formed when oil undergoes a process called hydrogenation, the hydrogenated fat can then be used for frying or as an ingredient in processed foods.

We should all try to have less saturated and trans-fats in our diet. Saturated fat can be reduced by choosing leaner cuts of meat or trimming off the fat, using low fat dairy products and grilling or poaching foods rather than frying or roasting them. As the negative effects of trans-fats have become more evident, their use in food manufacturing has declined. As a result, most people eat under half the recommended maximum of trans-fats, so saturated fat presents a much bigger problem. However, it is still worth checking labels and choosing oils that do not contain hydrogenated or partially hydrogenated vegetable oil.

Mono and polyunsaturated fats are better for us as they can help lower blood cholesterol. Sources of monounsatured fats include olive oil, nuts and avocados. Polyunsaturated fats can be found in rapeseed oil, sunflower oil, oily fish and nuts.

However, a fat is still a fat and to prevent gaining too much weight and increased risk of diseases in later life we shouldn’t eat too much of any type of fat – even the ‘good’ ones!

So how much fat should we eat?

Current recommendations state that no more than one third of our daily energy should come from fats. This works out at between 50-100g of fat per day depending on your nutritional requirements. Of this, less than 10% of our daily total energy intake should come from saturated fats (around 20g for women and 30g for men) and no more than 5g per day of trans-fats. Fat and saturated fat content of most food items can be found on the food labels.

Generally speaking, choosing plant sources of fat that contain mono or polyunsaturates where possible is best for heart health. But we should try to prevent over-consumption of any type of fat in order to prevent weight gain.

…Part 2 of ‘FATS’  explores fat makeup of different oils and spreads; which ones we should choose? I’ll also be looking at omega-3, omega-6 and the facts behind coconut oil.