BBC Horizon – Sugar v Fat. Who is the winner?

BBC showed a story of twin’s who embarked on an experiment to better understand who is the enemy to the human body…..Fat or Sugar.

It’s a common question with many different opinions of course and this story, by using twins, could be used as a fair experiment because the two were identical. Sounded reasonable and as it was introduced to me by family, I thought I’d watch it. It is shown above, so if you have a spare hour, take the time to watch it.

For the record, I am bias towards fat, so you will see that reflected below. But that’s not to say that I don’t like sweet tasting food. It’s just that now that I’ve cut refined processed sugar from my diet, my interpretation of ‘sweet’ has changed.

A really quick brief: The twins live in separate countries, England and the USA, where one eats a diet with very high levels of fat (no carbs, no sugar, no veg or fruit) and the other only sugar (refined sugar, carbs, fruit but no fat). The experiment was done for 1 month.

Watch the video for the finer details, but here’s my take. i focus below primarily on fat as I think this is the biggest misunderstanding amongst the wider population. Whereas everyone knows sugar is bad for you and I particular mean refined sugars.

After decades of bashing saturated fat throughout the 80’s & 90’s we were told to cut the fat from our diets. Low fat this, fat free that but the result was the complete opposite and we’re now fatter than ever before!

Fat makes us feel full more so than carbs so we eat less. That could be one contributing factor the twin on the fat diet lost weight. But some of that weight was also muscle which we want to protect. A few minutes of exercise each week would help that.

Once they introduced what they were eating, I almost switch it off, because it was completely flawed. There was no detail as to where the food came from.
– is the fruit organic?
– is the meat grass fed (and grass finished) or grain fed
– what are they cooking in? Vegetable oil?
– processed meat included? WHAT!?!?!?!?!
– the fat eater had no vegetables or carbs at all…who would ever promote this!?

It speaks of the brain requiring glucose to function properly and also of ketones being made available as an energy source. It took me almost 6 weeks to become fat adaptive so to create an experiment of only 1 month and expect the human body to change what it has used primarily as an energy source for decades is unrealistic. The thing that gets me is that the twins are themselves scientists!

I agree in that the brain gets most of it’s energy from glucose, but it also uses ketones as an alternative source and the ability for the brain to use this energy source takes some training.

AT a really high level, a ketogenic diet is similar to starvation, so that the body enters a metabolic state called ketosis. Most of us humans burn sugar; carbs are converted to glucose then transported and used as energy or stored as glycogen in liver and muscle tissue. When carbs are limited, generally less than 50 grams / day, the backup is the liver becomes the sole provider of glucose to the body including the brain.   The brain cannot utilise fat directly so the liver, as a backup, derives ketones from fatty acid in your diet or body fat.  These ketones are released into the bloodstream and used by the brain as fuel (amongst the body’s other organs).  The other thing to note about glucose is that excess protein is also converted to glucose is made out of the liver & kidneys called gluconeogenesis (

Having no carbs at all iss crazy and not what us ‘fat lovers’ would ever claim to do. What we do state is that you don’t need as many carbs in the diet as what is generally consumed on average today and you don’t need a lot for the body to transform them into glucose for the ‘brain to use’. Even for exercise I have some carbs, but it is all dependant on timing too. I eat most of my carbs before & after my workouts and not the same amount of food every day either.

Too many times we hear claims to eat a certain number of calories per day, but that doesn’t make any sense. Why would I eat the same amount of food on days when I’m exercising with a high energy output compared to days when I’m less active? Also where are my calories coming from? Cola has about 140 calories yet an avocado over 200…should I just have cans of cola instead!? I digress, but you get my point.

During the bike challenge in the movie, it was shown that the sugar burner had much more energy than the fat burner – this was always going to be the case in such a short time of being on the eating plans. As mentioned earlier, to become fat adaptive requires a lot longer than just a couple of weeks and to have zero carbs when exercising at a high intensity is just crazy! Sugar won…..obviously!

What I found when I burned sugar/glucose for energy, was that I generally needed to eat every few hours to maintain my blood glucose levels and I was disciplined to do it too. Now I eat only to maintain energy and sometimes go over 6 hours without eating with no problem at all.  It’s so much easier to get through a day when I don’t have to worry about eating every few hours, I don’t get tired in the afternoon nor do I have sugar cravings any more.

The first 2 weeks of removing all refined sugar from my diet were tough. The thing is I wasn’t previously unhealthy, well I didn’t look unhealthy, but as I got older (I’m almost 40) I could feel my body breaking down. That was also a result of other things which included overtraining, but the thing is when I started the higher fat plan about 8 months ago, I am now 2 kgs heavier, 3% less body fat and feeling great.

Not all fat is created equal.

Our bodies require Essential Fats (EF) and are named this because our body cannot produce them and we need to get them from food. All good fats are a blend of different types being saturated and unsaturated.

Unsaturated fats include mono & polyunsaturated fats where omega-6 & omega-3 are types of polyunsaturated fats. These are your essential fats.  Omega-6 is a proinflammatory and found in vegetable oils hence the reason to stay away from industrialised vegetable based oils.

Scientific experiments have shown that a ratio of omega-6 to omega-3 should not exceed 4:1 to avoid health problems. So here’s the scoop as to why I almost switched off the tv because it is so important to know where your fat is coming from. Omega 6 & 3 are important components of almost all cell membranes therefore unsaturated fat in the human body is greatly dependant on the food we eat

As an example of animal fat of Omega 6 & 3 ratios:  Grain fed beef can have ratios that exceed 20:1, whereas grass-fed (and grass finished) beef is around 3:1.

Now the ratio of fat between saturated and monounsaturated is about 40-50% for each and approximately 10% of polyunsaturated, all of which doesn’t really change between grass or grain fed beef. The difference is that the fat contains so much of the nutrients from what the cow ingests, it’s unfair to simply have the twin eating any type of fat, without knowing how the meat was produced?!

Grass fed beef has more antioxidants, vitamins and minerals amongst other benefits of Conjugated Lineoleic Acid (CLA). CLA has strong antioxidant traits and has been claimed to protective against heart disease, diabetes and cancer.

Chickens fed vegetables, insects, fresh green grass and dried fruit (not GMO!) have high levels of omega 3 with ratios of omega 6 & 3 of 1.5:1 whereas supermarket eggs have approximately 20:1!!!! It shouldn’t be a surprise then that our farmers are pressured to increase production in order to create a cost effective process at the detriment of nutrition!

There was a really surprising result form the test in the show and that was the twin who was eating primarily fat, was showing signs of being pre-diabetic. This was the complete opposite of what I and most thought would occur.

I do love that they finished with it isn’t just one thing… and the episode at least got that right.

The summary was pretty good:
* Avoid the processed food.
* Exercise/move

I hope by now you can see that fat cannot be classified just as fat, which is why this story from the BBC almost didn’t make it past the first 10 minutes on my tv. For me I run a 50% fat, 20% carbs and 20% protein ratio, on average, but on days of high energy output, the carb ratio increases.

I make sure I eat plenty of vegetables and is the staple for where I get carbs. A big bowl of vegetables, cooked in coconut oil is amazing! I try to get as much sleep as I can, as sleep is such a contributing factor to energy levels, recovery and overall health, that there isn’t enough importance given to it.

I don’t measure my food, but I’m fairly well in tune with my body that I know what does and doesn’t work and I eat purely on being satisfied. One things for sure though, REFINED sugar is nasty. Everyone agrees with that.



About onehealthyman

A passionate fitness and health nut stuck in a corporate world, and loving it. Born in '74 and finding a new way of eating, living and loving life with an amazing family. I've been training in Muay Thai, weights and anything fitness for over 20 I found a whole new world of healthy eating and hopefully I can share even something with one person that makes a difference to their life.
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