Sugar or fat, which is worse? This question has been discussed for some time now and dominated many a discussion whenever issues of dieting, health and weight issues rear their ugly head. It was certainly an important question asked in a recent BBC documentary. Two identical twin brothers – both of them doctors – go on a diet for a month. One on an extreme low fat diet, one on an extreme low-carbohydrate (low-carb) diet (not even vegetables are allowed!). A simple background to this documentary is that one twin gave up sugar, the other gave up fat. Unfortunately they end up mostly 'confirming' their preconceived ideas.
Obviously when there is only one person on each diet, chance plays a big role. But I think the findings were more or less what could be expected, it’s mostly the ignorant (or TV-drama) explanations I have objections to.
First thing first. Even though both brothers were at a fairly decent weight to start with, the low-carb brother lost the most weight: 4 kg (9 pounds) vs only 1 kg (2 pounds) for the low-fat brother.
As study after study show more effective weight loss on a low-carb diet, this should be no surprise. The loss of fat was 1,5 kg on low-carb (a good result in a month) and 0,5 kg on low-fat. Most of the rest was probably fluid. On a very strict low-carb diet you quickly lose a kilo or two of glycogen and water weight.
How much – if any – muscle mass the participants lost is impossible to know as the BodPod test only measures fat mass vs. non-fat mass (including water).
For testing the brain function of the brothers the producers chose to make them do stock trading with fake money. This shows that the producer is ignorant or just interested in a dramatic show. Why? Because short-term stock trading – without insider info or other illegal tricks – is a game of pure chance. It’s been convincingly shown that a trained monkey has a 50% chance of beating a well-educated stock broker. Why? Because it’s all chance.
In short, this test is rubbish, but the low-fat brother wins.
More interesting and relevant is that the low-carb brother complains of feeling 'thick-headed'. I’m sure he’s honest. Going on an extreme low-carb diet – without even vegetables – can absolutely result in problems concentrating etc. for a week or even more, before the body and brain adapts to burning fat and ketones. This problem can often be partially avoided by increasing the intake of fluid and salt. And after a week or two it’s normally gone.
For testing their exercise capacity the brothers do “long sessions of uphill cycling”. The low-carb brother predictably loses badly.
Why? Two things: the body needs weeks or sometimes even months to adapt to high-intensity exercise, using mostly fat and ketones. And even then you might need a little bit of carbs for explosive and anaerobic sports like this.
Finally the icing on the (diabetes) cake. The doctor claims that the low-carb brother has become 'almost' pre-diabetic by eating low-carb! The word 'almost' should actually be interpreted as 'not'. I wonder if the doctor knows the first thing about low-carb and diabetes. In fact I wonder how much he knows about diabetes at all.Worrying............. for a doctor!
The low-carb brother has a fasting glucose of 5.1 before the diet (normal) and a fasting glucose of 5.9 after the diet (normal). Did you catch the word 'normal' twice? Yes, that's right, a fasting glucose of up to 6.0 mmol/L is considered normal, at least in Sweden. It also varies significantly from day to day. If we tested the doctors’s own fasting blood glucose it might be 5.9 today and 5.1 tomorrow.
The result could be due to chance but sometimes the fasting glucose level actually gets slightly higher on an LCHF (low-carb, high-fat) diet, while the glucose levels during the day (after meals) is way lower. This is probably because the body is adapted to burning fat and so the need for burning glucose when fasting is lower. Thus you don’t get the same fasting 'dip' in sugar levels.
They also did glucose tolerance tests – a much more relevant test. But the result of the low-carb brother is never mentioned. I guess it was normal.
The fact that diabetes is effectively treated with a low-carb diet should tell us everything we need to know. You don’t get type 2 diabetes by eating a diet that can cure diabetes. And you certainly don’t get type 2 diabetes (strongly correlated to obesity) by losing 4 kilos of excess weight in a month.
The basic premise of the documentary was to compare an extremely high dietary fat intake to an extremely high intake of sugar and processed carbohydrates in a pair of identical twins. The programme introduced the idea that there are apparently polar views between Britain and the USA stating that Britain has been locked into the dogma that fat is bad for us, whereas in the USA the prevalent view is that sugar is bad for us. This is somewhat confusing from the start!
Indeed in the 1960's and 70's it was an American, Ancel Keyes, who dogmatically championed the theory that dietary fat, especially saturated fat, was the underlying cause of heart disease. Meanwhile in the UK during the same time period a prominent British nutritional scientist, John Yudkin, provided strong counter evidence that sugar was the real health challenge to the heart that should become the focus of public health guidelines. T
The dietary fat - heart hypothesis theory won out and the all too familiar low fat dogma has gone on to become the prevailing public dietary advice since 1980 in the USA and since 1984 in Britain. Whilst it is likely that in both countries there are opposing camps on this issue of fat or sugar as public enemy number one it seems strange that they would make this issue a division of opinion across nations. If anything the programme actually raises further questions regarding the chronic health problems associated with obesity and diabetes in the Western world.
Astonishingly both doctors were also both allowed to eat as much as they liked with no calorie control whatsoever. This created a problem in itself as demonstrated later in the programme that One twin was always hungry without much fat and protein in his diet and was eating all the time, whereas the other was almost never hungry and ate much less as a result of the powerful satiating effects of the high protein diet. This was demonstrated when in one meal the latter twin managed an impressive 825 calories of fat and protein before feeling totally overwhelmed and satiated, whereas the former twin was able to keep easily eating until he had consumed 1250 calories primarily from carbohydrates and still did not feel satiated.
These different calorie intakes would have created vastly differing internal biochemistry alone even without the differences in what composed the calories. It is blatantly clear that the two diets imposed simply had too many uncontrolled variables for the results to truly be meaningful, fair and comparative. From a scientific standpoint this really was poor to be honest and did not follow even some of the most basic principles of scientific investigation to provide worthy, valid results - namely control all the variables except the one difference to be investigated i.e. fat and sugar!
The documentary concludes that it’s not about fat or sugar, it’s about avoiding processed food with both fat and sugar in it. I’m sure that strategy would work fine for these two fairly fit brothers. It’s an excellent start. But it’s not enough for everybody. This is not really a revelation either. Sorry docs. This tidbit of information has long been known in food science circles and amongst the major food processing and manufacturing giants and is the primary reason that so many processed food products have both sugar and fats in abundance.
Perhaps one of the biggest mistakes that mankind has made took place years ago which was to seek out and find ways to extract and refine sugars from cane and beets in a mission to sweeten our food. Once the crippling taxes were removed from sugar in the late 1870’s and it became a highly affordable food stuff it has steadily increased in the human diet with average consumption now reaching 42kg per person per year in the UK and 65kg per person in the USA.
On the flip side there has always been a plentiful supply of fats in the diet, even in a natural diet, one only needs study the Eskimo, Native Americans or the Masai to find this out. However, naturally occurring sources of sugar in any long standing traditional diet is more difficult to find outside of seasonal fruit consumption and hard to obtain honey.
In people with obesity and diabetes studies convincingly show that low-carb diets are more effective. Most of the major sources of modern food that drive blood glucose up come from processed foods such as wheat flour, pasta, refined rice, cakes, ice cream, biscuits, pastries, crisps, pizza, chips, chocolate, confectionery, soft drinks, fruit juices etc. It is mankind and the food processing giants who have refined carbohydrate ingredients and mixed them with cheap vegetable fats like soy, corn and rapeseed oil to provide foods with high pleasure and hedonic response. The drive to make money out of food by business is responsible for our obesogenic environment. Nature is not to blame! Food is not to blame! Food processing on the other hand and those that service the food processing giants have a lot to answer for.
Finally, while a super-strict low-carb diet is not necessary for everyone and has possible side-effects (especially during the first week or two) it certainly do not result in diabetes. That’s just ignorant.
For more information go to: http://www.naturalfoodfinder.co.uk/horizon-sugar-fat-bad-science-blog
or http://www.dietdoctor.com/sugar-vs-fat-on-bbc-which-is-worse. For a highly trained nutritionist go to The British Association for Applied Nutrition and Nutritional Therapy at http://bant.org.uk/