bite my words

Dispelling nutrition myths, ranting, and occasionally, raving


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Low-fat vs low-carb

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There’s a lot to unpack from this Daily Mail article a friend alerted me to. The premise: a couple of identical twin doctors decide they need to lose weight. In order to determine which fad diet is better, one goes low-carb, the other goes low-fat. The fact that they are genetically identical and maintained similar levels of physical activity means that they assumed any differences observed would be due to diet. While there is merit to using identical twins in research studies it’s important to note that this was not a scientific experiment. One subject in each group doesn’t lead to robust findings. Other issues: obviously both men knew which diet they were on and there was no control group. So, this wasn’t good science but it’s still possible that we could learn something interesting from their little “experiment”.

Before we look at what they “learned” from the experiment there are a few things in the article that I want to touch on. Firstly, the headline states that “one twin gave up sugar”. Well, yes, but this twin also restricted all forms of carbohydrate, not just sugar. The twin who went on the low-carb diet thought that it would be effective because of the insulin hypothesis of weight gain.

Because these carbohydrates are highly refined, they tend to raise blood sugars and blood insulin levels quickly.  This will tend to cause weight gain and obesity.  This is known as the Carbohydrate-Insulin Hypothesis (CIH), and is the basis of the Atkins diet and many other low carbohydrate (Dukan) and very-low-carbohydrate diets (ketogenic diet). (1)

While it sounds convincing, we know this hypothesis to be incorrect. For one thing, there are many people/populations who consume high-carbohydrate diets and never develop obesity. For another, insulin on its own does not cause obesity (2). Minor quibble, really, but as doctors discussing weight loss they should have their facts straight. Obesity is complicated and there’s no smoking gun out there.

An important point that they make is:

…despite being doctors – I also have a degree in public health – neither of us knew much about losing weight and eating healthily. 

These topics fall between the cracks at medical school. Yes, we understood biochemistry and food metabolism, and knew a lot about the consequences of being overweight. But which diets work, why we eat too much and why losing weight is so hard don’t sit within any medical speciality.

Pity that they didn’t take the opportunity at this stage to point out that this means that assuming your family doctor will tell you if your weight is a health concern or that they are a good resource for weight loss are dangerous assumptions. If you are concerned about your weight being a health issue you need to speak up and voice those concerns. Ask for a referral to a dietitian who specialises in weight management or to a reputable weight management clinic. I really wish they would have mentioned the great resource that we dietitians can be for all things diet and nutrition.

As you may have guessed, both doctors lost weight during the course of their experiment. I hope that they were the only ones who were surprised by this outcome. Naturally they lost weight; they were both on highly restrictive diets, they were both active males, and this was done over a very short period of time (one month). Imagine trying to sustain a diet with the barest minimum of fat or no carbohydrates for the rest of your life!

Fortunately, the doctors reached a conclusion that I actually agree with! That: “For any diet to work you have to be able to keep it up for the rest of your life.”  As I’ve said many times before: to see sustainable weight loss you need to make sustainable changes.


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Is sugar the “new tobacco”?

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The headline reads “Why are health experts calling sugar the new tobacco?” Because it’s catchy and makes for great headlines, duh!

I know that a lot of people are going to be pissed off with me for not taking up the cause and demonizing sugar. Sorry guys. I agree that most of us consume too much sugar (and too much of anything is a bad thing). I agree that excess sugar can cause cavities. I agree that the vast majority of us like sweet foods. However, I don’t believe that sugar is truly addictive… There is a difference between addiction and desire. Just because rats like oreos and sugar “lights up pleasure centres” in our brains doesn’t make it addictive.

I keep seeing claims that our bodies process calories from white sugar differently than calories from other foods. This makes no sense. The common definition of a calorie (technically a kilocalorie) is: the amount of heat required to raise the temperature of one kilogram of water one degree Celsius (1). There is no way for your body to differentiate between “types” of calories. There is only one type! Your body also can’t distinguish between sucrose in white sugar and sucrose in an apple. It is a chemical compound. It is what it is.

Calling on the food industry to reduce sugar content of foods is a dangerous proposition, in my opinion. Remember when we asked food manufacturers to reduce fat content? They added salt and sugar. Remember when we asked food manufacturers to reduce sodium? Not that much ever came of this. Point being, when they take something out they put something else in to replace it. We now know that fat is not inherently bad for us, nor is sodium, nor is sugar. No one of these things alone is causing obesity. Rather than asking food manufacturers to reduce the sugar content of their foods we should be calling for less heavily processed foods.

Sugar is not the new tobacco. It’s the new scapegoat in the obesity wars.


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Smart Swaps: Not so smart

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Public health is hard. I get it. I was there. It’s hard to come up with ways to improve population health. Nutrition is a particularly difficult area to address. After all, it’s not like smoking where you know that it’s unhealthy and your goal is to convince people to quit (or never start). Nutrition and our relationships with food are complicated. Unfortunately, in most cases, public health campaigns fall flat. I’m afraid that’s going to be the case with the latest Smart Swaps campaign in Britain.

As a few people point out in this news article, money could have been better spent revamping the food system to encourage healthy choices. I’d also like to suggest core curriculum for students so that food skills can be learned young and shared with the entire family.

Beyond the issues raised in the article (i.e. that resources could have been better used elsewhere) I have a bit of an issue with the smart swaps included in the campaign. They seem to be predominantly focussed on calories and weight loss. Yes, there’s swapping sugary cereal to unsweetened cereal, and swapping  sugar sweetened beverages to unsweetened beverages. Not bad swaps. But how about swapping whole milk to low-fat milk, and then swapping that for skimmed milk?  Or swapping butter to lower-fat butter or spreads and cheese to reduced-fat cheese? Yes, that will save you calories but that doesn’t necessarily mean you’re making healthier choices. Fat is not the enemy. Too much of anything is the enemy. Too much highly processed convenience food is the enemy. Not cooking (using minimally processed ingredients) is the enemy. These simple swaps are too simplistic to address the growing problem of obesity and malnutrition.


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Does fat cause breast cancer?

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I don’t even have to read the study about high-fat diets causing breast cancer in teenage girls to say that it’s essentially meaningless. Just reading the news article pissed me off. Why? Because the headline reads: High Fat Diet Tied To Accelerated Breast Cancer Development In Teenage Girls. Oh no! Maybe we were wrong (again!) that fat isn’t the demon food we once believed it to be. Read a little further… “the researchers fed a group of female, pubertal mice a high fat diet”. Wait… So this study didn’t actually study human teenage girls? Well, how much fat is “high-fat”? And what type(s) of fats did these mice eat? Perhaps I do need to turn to the actual study after all.

Mice on the low-fat diet were given 10-12% of total calories from fat. Mice on the high-fat diet were given 60% of total calories from fat. The fat was from corn oil and lard. Mostly lard. Up to 54.5% of total calories came from lard. Can you imagine eating more than half of your calories in a day from lard? Presuming an average teenage girl needs 2, 000 calories a day (give or take a couple of hundred) that means that about 1, 080 calories come from lard! That’s more than 100 grams of lard. And that’s not even counting the calories from the corn oil!

The study found that the high-fat diet affected genes in the mice associated with breast cancer. Interestingly, the high-fat diet had no effect on weight (more evidence that calories do matter). Their conclusion was that a high-fat diet can increase the risk of breast cancer in girls, independent of weight status.

My conclusion: humans are not the same as mice. If you are a mouse eating obscene amounts of lard and corn oil on a daily basis you might have cause for concern. Even if you’re not a mouse, that’s too much lard.

 


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Fear of fat

Last week an article in the Globe and Mail discussed recent research indicating that saturated fat is not the heart attack waiting to happen that we believed it to be for the last couple of decades. Great news for butter lovers! As an aside, my original tag-line for this blog was going to be “real dietitians eat butter”. Bad news for many health promoting organizations and for many consumers.

I say it’s bad news for many organizations because messages need to be updated and when you’re dealing with slow-moving bureaucracies such as Health Canada, this often takes some time to occur. In the meantime, this becomes bad for consumers because it’s difficult to know which messages to believe. When the government is telling you to choose margarine and others are telling you to put several tablespoons of butter in your coffee, who to believe?

Personally, I’ve always taken the stance that just because a little of something is good for you it doesn’t necessarily follow that a lot of it is better. Too much of anything is bad for you. Just because we’ve figured out that saturated fats are not likely to cause heart disease doesn’t mean that you should make all of the fat in your diet saturated. Variety is both the spice of life and the foundation of a healthy diet. Go ahead, use butter in that recipe, spread a little on your roll, but also continue to include other fats such as olive oil, nuts, and seeds.

We also need to remember that just because fat doesn’t automatically turn to fat in your body doesn’t mean that it won’t. Fats still have more calories by weight (9 kcal per gram) than other macronutrients. If you consume more calories than your body needs you will gain weight and consuming calorie dense foods (such as those high in fat) makes this easier to do.

There’s no need to fear the fat, be it saturated or unsaturated, but there’s also danger to embracing it to the exclusion of other nutrients.

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