DietNet - Low Carb vs Low Fat

Somebody said to me in an email recently "Everybody knows that a low fat, high carbohydrate diet is the most healthy." My reply? "In my experience, something that is known by everybody is almost invariably wrong". Sadly, this is a situation we frequently find ourselves in today.

The low fat myth has become so accepted by western society that many health professionals, personal trainers, government agencies, societies supporting those with serious illnesses and most of the general public believe that lowering your fat intake and increasing your carbs, especially grains, is a healthy way to eat. But it is simply not true. It was never proven - it was a hypothesis that someone came up with about 30 years ago, and it was repeated so many times that everybody came to believe it.

The tragic part is that over the last 30 years, while people have been leaping on the low-fat bandwagon, there has been an increase in obesity, heart disease, diabetes, cancer and many other illnesses. This is not a coincidence. The only studies that show any improvement in health from this kind of diet are short term. There are no long term studies that support this theory.

Firstly, let's look at why a low fat diet might show a short term improvement in health. The quality of food available to us in modern times is shocking. With our busy lifestyles, we rely heavily on processed foods for quick meals. Takeaways are eaten much more frequently than previously, and children and teenagers breakfast on potato chips and chocolate while waiting for the school bus. So, many people have a poor diet. When you go to a doctor with a health problem, he or she may put you on a low fat diet, with an emphasis on fruit, vegetable and grains. You may stop eating takeaways and eat more natural foods. You get an improvement in health from the extra nutrients in the fruit and veges, but more importantly from the decrease in overly processed foods.

Unfortunately, this often doesn't last. After a while, the lack of essential fatty acids and inadequate protein start to catch up with you. Without enough building blocks, your body's processes start to slow down. At the same time, the higher intake of carbohydrate raises your insulin levels, which eventually leads to other health problems, including Syndrome X. The imbalance in your macronutrient intake also causes an imbalance in your micronutrient (vitamins & minerals) intake. This leads to a whole host more problems.

To cater for the demand for low fat foods, manufacturers are now producing many items that can be advertised as low fat. Trouble is, when you look at the label, the high carb content is often comprised of sugars of one kind or another. I recently looked at the ingredients of a box of cereal that had the NZ Heart Foundation tick on the front of it and discovered it had 6 different types of sugar in it! Even some of the more conservative health "experts" agree that a diet high in sugar is unhealthy. Foods manufactured in the US often contain high fructose corn syrup as the main sweetener. This is one of the mose dangerous sweeteners around.

As if this wasn't enough, a diet high in grains causes a further set of problems. Grains are a comparatively new food to humans. Until we learnt to grind and cook them, we couldn't eat them at all, due to their anti-nutrient content. After we began to cultivate grains, about 8-10,000 years ago, our health deteriorated. This is because they were simply not a suitable food, despite us learning how to process them so that they could be tolerated. Eating grains can lead to leaky gut, food intolerances and autoimmune disease. The Protein Power Lifeplan has a very good explanation of this process.

As you know if you have read other parts of this site, I don't believe in a one size fits all approach to diet. While we all need a balance between protein, fat and carbohydrate, this balance seems to vary. In our household of only two people, this is illustrated beyond any possible doubt. (For more information, refer to the metabolic diets section.)

This means that some people tolerate a diet lower in fat and higher in carbohydrate than others, and still keep good health. This may be one of the reasons that the myth has been accepted for so long. We see people who have success with a low fat diet, and think it's our own fault we have failed on it. But the people who do well on a lower fat diet still have to be careful to get enough fat and protein, or health problems are likely to develop further down the track.

Another group of people who may find a higher carb diet suitable is endurance athletes. As they need a huge amount of fuel, they can eat more carbohydrate without the health problems caused by eating more fuel than you can burn. But they also have higher fat and protein requirements, as their bodies have more regenerating to do. So in this case, higher carb still doesn't mean low fat.

My own story of contracting chronic fatigue illustrates how a diet too low in fat can undermine your health. But more importantly, it shows that you can be going along quite nicely thinking all is well, and all of a sudden you get sick. In other words, whatever diet you are on, be aware of any signs that may indicate something is wrong.

But what about the dangers of a low carb diet? Are there any of those? Of course there are. Any diet taken to an extreme can be unhealthy. But the reaction that greets anyone suggesting a low carb diet is often a knee-jerk one, without an examination of the facts.

Surely a diet high in saturated fat has been proved to cause high cholesteral and heart disease? Actually, no it hasn't. Studies show that a diet higher in saturated fat correlates to better health.

I've noticed that many low carb diet plans have been produced by medical doctors, who have been using these principles with their patients. They see an increase in health in the vast majority of their patients, on a long term basis. While this cannot be held up as proof that the principles are right, it seems to be a good indicator that low carb is more successful than low fat for many people.

In summary :

We all have different dietary requirements and the correct balance between protein, carbohydrate amd fat can vary between people. But protein and fat are vital building blocks for our body, whereas carbs are only used for fuel. So we must all be careful to get enough of them.

Some short term benefits from a low fat diet have been documented, but none have held up long term. The reasons for failure of low fat diets include :

Inadequate protein and fat in the diet mean our bodies can't rebuild properly
Too high a carb intake leads to high levels of insulin in the blood, which causes many diseases
Eating foods advertised as low fat usually means a diet high in sugar
Reliance on grains as a dietary staple leads to many chronic health problems
Deviating from the diet of our ancestors means that we don't get all the vitamins and minerals we need, resulting in dangerous imbalances

But the most convincing argument against a low fat diet is simply that it has failed. We eat less fat than ever before and our health is much, much worse.

Studies, and the experience of doctors treating patients with a low carb diet, both indicate that these seem to be far more successful. Possible downsides to be aware of include :

Eating too much soy or dairy
Eating too much protein and fat, rather than the recommended adequate amounts
Not eating enough different fruit & vegetables to cover vitamin and mineral requirements (supplementation is usually recommended)

For both plans, you should make sensible choices within the scope of the plan. Avoid junk food, processed foods, margarine, cheap vegetable oils, fried foods and sugars. As always, monitor how you are feeling, and don't continue with any plan that makes you feel unwell (beyond a settling-in period)