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high-carb-Chris (left) and high-fat-Xand (right)

Sugar v Fat: Debunking the Latest Attack on Low-Carb Diets

Has the recent media-splurge on nutrition left you confused?

Don’t worry.

Biases exist everywhere, but it’s easy to see past them when you take a closer look.

We’ve lived through decades of fat demonetization, and recently carbs have taken center stage as the macronutrient of Lucipher.

As we know, neither one of these macronutrients are bad in themselves, despite fashionable trends. The greatest danger comes from what our food manufacturers do to them and eating them in abundance

Xand (left) and Chris (right) Van Tulleken test to see which works best for them: a no-carb diet or a high-carb diet.

The BBC documentary Sugar v Fat, was presented by two identical twins, doctors Chris and Xand Van Tulleken, who both went on opposite diets for a month. Chris ate very little fat, and Xand ate no carbohydrate whatsoever. Xand summarized his experience and opinions in an article for the Daily Mail.

While it has an air of revolutionary new findings, they wound up saying what we’ve been screaming from the rooftops of the internet for years:

Stay away from processed food.

Professor Paul Kenny, who makes a mark in the second half of the show, has tested different ratios of fat to sugar on rats, to see which they find most palatable. It turns out that a food which has a ratio of 1:1 or equal parts of both, (e.g. standard cheesecake), had the most addicting effect on the rats, and made them gain weight the fastest.

The little guys lost all interest in healthy food, and would constantly graze their hunk of junk all day long.

Sound familiar?

It seems that tests run on human beings return similar results. Not scientific tests, but economic. Sales of Krispy Kreme’s simple glazed donuts are higher than any other variety. This is a correlation, so we can’t say for sure what the reason for our preference is, but it may have something to do with the fact that it is the only variety with a 50/50 split of fat and sugar.

This is old news.

sugarvfat cheesecake rat
Prof. Paul Kenny’s rats became powerfully addicted to cheesecake which had a 50/50 ratio of fat to sugar.

Companies have been combining fat and sugar ever since the birth of the industrial food industry to encourage people, like the lab rats, to graze on their products as much as possible, and to lose interest in other food.

The end of the documentary makes a good point about the state of our food culture now. Dr Susan Jebb told the presenters, “It’s astonishing that any of us stay slim in a world like this … you have to exert quite a level of dietary restraint if you’re not going to effectively just sleep-walk into obesity.”

The closing message is that processed foods often combine carbs and fat into a lethally addictive combination, to stay away!

Sounds like a good message so far.

The Damage It Has Done

People are leaving this documentary confused.

While the final point is to cut down on foods that combine carbs and fat, the rest of the show tries to convince us that limiting either one is dangerous.

The high-fat twin, Dr Xand, stuck to a 0% carb diet that had him “remove all fruit and veg” because “they have carbs”, while the high-carb twin, Chris, kept 2% of his calorie intake from fats because “you need some fat to survive”.

You certainly do need fat to survive! But what does Xand think he’s doing cutting out all vegetables?

He said he “felt slow and tired” at the end of the month. I’m not surprised.

If they wanted to be scientific, keeping 2% of his calorie intake from carbs would have made the playing field much more even. There’s a big difference between 2% and 0%.

If you want to lose weight and reduce inflammation, you can do so by cutting carbs, but maintain at least 30g a day, and get them from vegetables. That way you’ll also be benefiting from the vitamins and minerals that are difficult to obtain from animal sources. This approach works consistently, and it’s not the approach Xand took.

In the companion article, written by the no-carb Dr Xand, we read his summary of the insulin hypothesis (that eating carbs triggers insulin to store energy as fat), and that this “undercuts the most basic idea about weight gain: that if you eat more calories than you burn, you gain weight.”

I shake my head in disbelief.

Taking sides where there’s no need seems to be a universal human impulse. Don’t think that we medical professionals are any different.

The insulin hypothesis never did undercut the idea that you have to store more energy than you use in order to gain weight. It simply states that refined carbohydrates encourage your body to store energy rather than use it, which makes you hungry and lures you into eating more.

What it does undercut is the woefully ineffective weight-loss method of forcing yourself to eat less and exercise more, without paying any attention to the quality of your food.

You can lose weight on a high-carb diet by restricting calories, but it’s torturously difficult.

You can see this effect on the high-carb twin, who “never felt full, so was constantly snacking”.

The no-carb twin, conversely, “was never hungry”.

Only a few of the foods pictured here were allowed to Xand on his highly restrictive no-plant diet.

What Your Doctor Doesn’t Want You To Know

“But here’s the problem,” Xand wrote. “Despite both of us being doctors … neither of us knew much about losing weight and eating healthily. These topics fall between the cracks at medical school.” (from the article)

Very true. In fact, the problem is more sinister than that.

Investigations into funding of medical education “found that 59% of practice guideline developers had a financial relationship with a company that made a product addressed by those guidelines.” (emphasis mine)

This means companies that produce, for example, statins, payed money to the man who wrote the text-book which taught your doctor that if you have high cholesterol, he should put you on a course of statins.

Unfortunately, the same financial incentive doesn’t exist for the advice of eating an optimal diet.

This may help explain why nutritional therapy is so poorly taught, despite how safe and effective it is in treating chronic disease.

The Insulin-Resistant Elephant in the Room

What about all that fat causing Xand to approach pre-diabetes?

Thought I’d be tempted to gloss over that part, didn’t you?

Never! Especially not when it was the strongest demonstration of bias in the whole show.

First we’ll start with the “amazing” results that would seem commonplace to anyone in the low-carb or paleo diet space.

Twin Chris narrates some close up shots of needles and blood dripping in tubes:

blood_tube“We thought that because Xand was eating so much fat on his diet, his levels [of cholesterol] would be much higher. What was amazing is that they were nearly exactly the same as they were at the start of our diets.”

No surprises there then.

The scene goes on to show them having their fasting glucose and insulin sensitivity tested.

The results for carb-binger Chris were taken surprisingly well. Their lab technician, Richard Mckenzie, said:

“Your body’s ability to produce insulin has improved.”

Hold the phone. It’s an improvement for your pancreas to readily flood the blood with huge amounts of insulin? He goes on to explain:

“His body has probably just got used to dealing with the sugar … and therefore responding by producing insulin.”

Chris seems to be taking this as a positive:

“A bit like if I’d been drinking a lot for the month, my liver would up-regulate the enzymes to deal with the alcohol … because I’ve been eating loads of sugar, I’ve become better at managing it.”

Richard is careful not to let him get carried away, and corrects him with a cautionary tone:

“You’re better at producing insulin … In the short term it might be good, but in the long term it might produce a problem.”

This essentially means that when you drink a litre of Gatorade, you won’t feel the effects of the drink as much if your body can churn out a ton of insulin. The long-term problem he managed not to name is insulin resistance.

Then the high-fat Xand got some seemingly bad news. Richard tells him:

“What’s worrying is your body is not responding to insulin as well as it did. If you eat too much fat, it can stop your body responding to insulin and it can also tell your body to produce more glucose.”

He goes on to tell him that his blood glucose is now 5.9mmol/L, which is 0.2 away from pre-diabetic:

“Eventually your body will stop producing insulin if you carry on down this path.”

Okay, let’s see how much of this is quackery, and how much is legit.

I’m afraid there is some evidence that saturated fat (only) can worsen insulin sensitivity. However, there is also evidence that suggests it does nothing.

The science is not conclusive either way.

Richard seems to be listening only to the evidence that supports the tired old idea that fat makes you sick.

Secondly, why is it a bad thing that Xand didn’t flood his blood with so much insulin when he gave himself the big spike in sugar? Chris was right. It’s like a T-totaller having her first drink. She’s likely to get light headed pretty quickly, because her liver is not used to dealing with the toxins in the drink.

Of course it wouldn’t suddenly produce a ton of it at the drop of a hat. Of course his body was producing more glucose – he wasn’t eating any!

Richard’s idea that all this meant Xand would one day stop producing any insulin was pure conjecture. He was producing less insulin because he needed less, not because the system was dying.

The one legitimate concern was that Xand’s fasting glucose levels seemed to have risen. Since this was so far from a controlled trial, we can’t know that the fat in his diet was causing it through a reduction of insulin sensitivity. There are too many variables. We only know it’s possible.

We also can’t know if these levels would have kept rising if he had kept it up for another month. They were still in a healthy range, so maybe his body had simply settled on a new norm.

The implication that he was on a freight-train to full blown diabetes was, again, reactive conjecture.

Possible, but not scientific to say it was definitely happening, let alone decide what caused it.

This Documentary Can Change Your Life, Without Changing Your Mind

It’s always inspiring to see people taking action and experimenting with different lifestyles to see how it affects them.

The experiences of these two identical twins does not directly translate into the experiences of you and me. It was self-experimentation with a buddy. Any one of us could do the same experiment, only it would take us two months to get the results of both diets, rather than one.

In fact, maybe we should.

Looking at someone else’s results will not tell you anything about how you will respond. All it can do is pique your curiosity.

And that can be enough to change a life.

If you’d rather base your life decisions on scientific analysis, (rather than on vague implications, ruthlessly edited and presented on a background of manipulative music), then take a look at analyses like this one, which looks at 23 gold-standard scientific studies, all comparing the results of low-fat vs low-carb diets.

We don’t need an opinionated piece of theatre to learn what we need to know about food. We’ve already proven which is worse.

Be inspired to run your own self-experiments, and remember that the types of carbs and fats make a huge difference.

Context matters, and a natural, whole-food context wins every time.

Are you considering going on a low-carb or low-fat diet? Drop your questions and insights into the comments below, or enter your email address in the box below to get access to me directly.



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