Carbs or Fat – which one should we eat less of?


Since 1977, Health Canada and Canada’s Food Guide have been promoting a diet which is high in carbs (45-65%) and low in fat (20-35% ) and which recommends that no more than 7% of fat comes from saturated fat — with the goal of lowering heart disease.

As elaborated on in an earlier blog, prior to 1977, the obesity rate [measured as Body Mass Index (BMI) ≥ 30 kg / m2] of Canadian adults was <10% and in 1978, only 15% of children and adolescents were overweight or obese.

As a result of lowering dietary intake from fat and increasing it substantially from carbohydrates, what happened to obesity statistics? Diabetes statistics?

Obesity became an epidemic.

In adults the prevalence of obesity [body mass index (BMI) ≥30 kg/m2] went from 10% in 1970-72 to 26% in 2009-11! In children, that rate doubled to 29% of children and adolescents being overweight or obese by 2007 and by 2011, obesity prevalence for boys was 15.1% and for girls was  8.0% in 5 to 17 year olds.

Based on waist circumference, 37% of adults and 13% of youth are currently considered abdominally obese.

Diabetes rates almost doubled.

In the 1970s, the rate of Type 2 Diabetes in women was 2.6% and 3.4 % in men, in the 1980s that number rose to 3.8% for women and 4.5% for men.  In the 1990s the rate was almost double what it was in 1970; 4.7% for women and 7.5% for men.

Now get this: Type 2 Diabetes contributes to increased risk of heart disease.

So in an effort to reduce rates of heart disease by lowering fat intake and increasing carbohydrate intake, rates of Type 2 Diabetes doubled — which in turn, raised the risk of heart disease! Ironic.

If eating a high carbohydrate, low fat diet is associated with higher rates of obesity which in turn results in a higher incidence of Type 2 Diabetes, what is the option? Isn’t it also a problem to eat a low carbohydrate / high fat diet… isn’t a high fat diet bad for you?”.

This is the question that we will begin to answer in this article and conclude in the next one.

Are all fats the same? Is extra virgin olive oil in the same category as bacon? Or fish oil as lard?

The Health Canada guidelines recommend eating low fat dairy products, lean meat and using a “small amount – 2 to 3 tablespoons (30 to 45 mL ) of unsaturated fat each day. This includes oil used for cooking, salad dressings, margarine and mayonnaise“.

1. We are told to use a small amount of unsaturated fat per day; what is an unsaturated fat and are they all the same?

2. Is the fat in dairy products and meat “bad” for you?

I am going to answer the first question in this article and the second question in the next one.

1. What are the different type of fats.

There are two main classes of fats — saturated fats and unsaturated fats.

Unsaturated fat can be further classified as polyunsaturated fats and mono-unsaturated fats. Polyunsaturated fats include everything from omega-3 fats from fish oil to the fat found in omega-6 fats found in canola oil and corn oil. More about what makes it an ‘omega-3’ or ‘omega-g’ below. Omega-3 fats, especially the long chain ones from fish oil (e.g. DHA, EPA) are heart-healthy and are anti-inflammatory and have been found to be protective against heart disease. Refined seed oils that are high in omega-6 fats are pro-inflammatory.

Monounsaturated fats such as those found in avocado and nuts or cold-expressed from olive oil or avocado or nuts and seeds are considered by Health Canada and the writers of Canada’s Food Guide as the healthiest (and thus, preferred) kind of fat.

We’ve been told to eat a “low fat diet” but are all fats the same? Are omega-3 fats from fish to be lumped together with fat from bacon? And if we eat a diet low in saturated fat, will our “bad” cholesterol (LDL) go down?

Most people have heard that of the fats taken in from the diet, saturated fat is “bad” for you and mono-unsaturated fat and polyunsaturated fat is “good” for you.  Before we deal with whether this is true, let’s define what these are.

There are some basics that we need to cover, to ‘follow’ the discussion as to whether saturated fat in the diet results in high LDL cholesterol and high Triglycerides (TG). I’ll try to make this much less painful than it may have been when you first learned this.

  • fatty acids are molecules made up of a carbon backbone.  Think of it like a train with cars connected together.  Actually think of it more like “fuselage” of a plane (which will become clear as to why, below). The body is made up of carbons all in a row.
  • if there are no double bonds in the carbon chain, it is a saturated fatty acids because something can bond at every carbon along the carbon chain.  Think of those molecules that bond to a carbon as “wings” sticking off the fuselage.
  • if there is one double bond in the carbon chain, it is an unsaturated fatty acid. It is “unsaturated” because no other compound can bond where the double bond is. So it can have “wings” every where else along the carbon chain (which makes it unsaturated) but not at the place where the one double bond is.
  • if the carbon chain has more than one double bond, it is called a polyunsaturated  fatty acids (PUFAs).
  • there can be a double bonds off one of the carbons in the carbon backbone chain.
  • where the double bond off the carbon backbone is located determines whether it is an omega-3 polyunsaturated fatty acid or an omega-6 polyunsaturated fatty acid.
  • all omega-3 fats have their first double bond in the same place on the carbon chain (away from what is called the ‘carboxyl’ end).  All omega-3 fats have their first double bond starting at the 3rd carbon (away from what is called the ‘carboxyl end’).
  • all omega 6 fats have their first double bond starting at the 6th carbon (away from the carboxyl end)

That’s pretty well all the chemistry you need to know.

So we’ve heard that we should decrease our intake of all fat, especially saturated fat as it leads to high LDL cholesterol, high triglycerides (TG) but is that true?   2. Is the fat in dairy products and meat “bad” for you?

3. Is saturated fat in the diet the only source?

Spoiler alert!

Our bodies not only make fat, they synthesize saturated fat!

We will cover the making of endogenous (“in the body”) saturated fat in Part 2, coming soon!

Meanwhile, remember that most people’s extended benefit coverage rolls over a the end of the year; which is coming up in only 5 weeks and most plans cover visits to a Registered Dietitian.

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