UK Government’s ‘fat tax’ idea is not based on science and is unlikely to work

Burgeoning rates of obesity and chronic disease here in the UK have caused our Government to consider and then implement a number of initiatives designed, we are led to believe, to assist us in our attaining and maintaining of a healthy weight. It is considering, for instance, putting a tax on fatty foods. The idea of a ‘fat tax’ is to discourage the eating of fatty foods that will then lead to people being less fat. The idea is elegant, but it’s also based on potentially faulty premises.

The first, and our Government is apparently aware of this, is whether making foods more expensive will actually lead to meaningful reductions in the purchasing and ingestion of these foods. I am not aware of any evidence that has looked at this specifically. However, even if we have not good evidence in this area, I wouldn’t think that this would stop our Government bringing such a tax into being. The UK Government, like many governments around the world, does not appear to be particularly inclined to base food policy on science, after all.

By way of example, I’d like to explore the other potentially faulty premise behind our Government’s latest wheeze – the idea that fat is fattening.

Because fat is called, well, fat, there is a natural tendency is to assume that the one sure way to get fat is to eat some. Digestion and metabolism of fat is quite a chemically complex process, and we would be hasty to assume that eating fat is somehow akin to injecting it directly into our fat cells. Apart from its name, the other thing that is used to incriminate fat is the fact that, per gram, it contains about twice as many calories as either carbohydrate or protein.

However, this again ignores the fact that different types of food can have different effects on things like appetite, metabolism and hormone levels that mean that eating something calorific is not necessarily fattening.

Here are just a few reasons why eating fat may not be necessarily fattening:

1. Not all calories have the same propensity to cause weight gain

Imagine your body is a lit barbeque, and you put two fuels on it: charcoal briquettes and petrol. Do they burn at the same rate? Of course not. Could food have a similar effect in the body? In a previous post (here) I wrote about a study in mice that found that even for a set number of calories, a high-fat diet had distinct advantages in terms of weight management.

Studies in humans have, generally speaking, not found a so-called ‘metabolic advantage’, but this may be because the studies used to assess this have failed to show one (due, for instance, because the study did not go on for long enough, or people ate other foods in addition to their prescribed diet).

2. Fat might help to sate the appetite, causing people to eat less overall

Fat stimulates the secretion of the hormone cholecystokinin, which slows the rate at which the stomach empties itself, and can prolong feelings of fullness. Studies have found that, for a given number of calories, fat can be more effective at sating the appetite than carbohydrate.

3. Not all fat that is eaten is necessarily absorbed from the gut anyway

Studies show that when fatty food is eaten, not all of it gets absorbed into the body. Some ends up going straight down the toilet.

4. Fat that is eaten doesn’t necessarily end up getting stuck in the fat cells

For fat to get fixed in the fat cells, three molecules of fat (called fatty acids) are combined with a molecule of something called glycerol, which is derived from sugar. In other words, the more sugar one eats (in the form of sugar but also starch), the greater the tendency will be for fat to get ‘fixed’ in the fat cells.

At least some of these ideas here are quite theoretical, and will never really inform us regarding the likely ‘benefits’ of a fat tax. What we require here are ‘intervention’ studies. Essentially, what happens when people eat less fat. If fat is fattening, then this approach should be effective for the purposes of weight loss, right?

When low-fat diets have been tested in research, they are usually of the ‘calorie-controlled’ variety. This means that in addition to restricting fat, individuals are required to eat less (in terms of calories too). Some studies have pitted low-fat calorie-controlled diets against those that are calorie-controlled but not necessarily low in fat. If fat is truly the demon in obesity, we would expect to see two things:

1.     Low-fat diets out-perform diets in which fat is not restricted as much

2.     Low fat diets lead to weight loss in the long term

The available evidence in the area was reviewed by an international group of researchers known as the Cochrane Collaboration in 2002 [1]. The researchers were particularly interested in the ability of participants to sustain weight loss over a relatively long period of time.

Here’s what they found:

Higher-fat diets tended to lead to enhanced weight loss over time compared to those lower in fat.

On average, 18 months on a low-fat regime led to a net gain in weight (while those on a higher fat diet lost some weight on average).

This study was withdrawn in 2008, on the basis that it was out of date, and that the authors had no intention of updating it. Back in 2002 the evidence clearly showed that low-fat diets are not effective for the purposes of weight loss, and no significant evidence has come to light since then that would cause us to draw any other conclusion.

It seems to me that if the Government is considering taxing fatty foods, it should be pretty sure that fat is fattening and that eating less fat really does help combat obesity. The reality is, though, that the evidence does not support either of these premises.

There is however mounting evidence that carbohydrates that disrupt blood sugar levels and insulin (including grains) are a potent factor in the burgeoning rates of obesity seen here in the UK and other countries. In my blog on Wednesday I referred to the research presented in my latest book which reveals that, overall, low-carb eating is much more effective than low-fat dieting in terms of weight management. This superior effectiveness comes even though low-carb diets in the research are usually not restricted in terms of calories (though low-fat diets usually are).

In my opinion foods to be most wary of and consider taxing include those carbohydrate-based ones that are highly disruptive to blood sugar and insulin including bread, potato, rice, pasta and breakfast cereals – that’s right, some of the very foods that our Government have been encouraging us to fill up on for decades now. For Governments to act in accordance with the science regarding obesity would mean tacitly admitting that the high-carb diet they’ve been pushing for the last 40-odd years is a big part of the problem.


1. Pirozzo S, et al. Advice on low-fat diets for obesity. Cochrane Database Syst Rev. 2002; (2): CD003640

10 Responses to UK Government’s ‘fat tax’ idea is not based on science and is unlikely to work

  1. Chris 11 November 2010 at 9:52 pm #

    Great summation, Dr Briffa.

    I wonder am I correct to add;

    5. As part of a meal the fat content lowers the aggregate glycemic load of the meal as a whole. This tempers the GL from the carbohydrate within the meal and may therefore reduce the post prandrail spike in insulin with the benefit of keeping insulin response lower and flatter. Equally the fibre content, soluble fibre in particular, can help to temper, or ‘buffer’, digestion and the transference of nutrients, including glucose from carbohydrates, into the blood, again contributing to the stability of blood sugar and insulin levels.

    But as much as quantity of fats may have a bearing on obesity I live with an expectation that the ‘quality’ of fats is crucial. Process has largely engineered soluble fibre and ‘solidity’ (reference to a previous post) out of ‘food’ and engineered in the wrong kind of fats and oils. I doubt Health Secretary, Andrew Lansley, is commensurate with the postulation.

  2. helen 12 November 2010 at 11:00 am #

    Ha our Labor government is talking about the same thing here in Australia………….seems there are no new ideas under the sun!! It seems to be the way of things at present everywhere in the world ….we have a problem ….what shall we do?….I know lets tax it!!!!

    Born free…….taxed to death!!!

  3. Victoria 12 November 2010 at 1:38 pm #

    I absolutely agree with you about fats. But isn’t it important to distinguish between simple and complex carbohydrates?

    What about sugar: isn’t that one of the worst culprits? What about a tax on sugar?

  4. Stephen Hoyt 12 November 2010 at 5:31 pm #

    Here is North America the discussion of government control on “food” is taking place too. In America and in Canada, over 25% of our younger population is obese and fast foods with high fat, carbs and sugar content coupled with flashy gifts as buying incentives may be part of the problem.

    History tells us that government controls may not be the best solution; a conversation I listened to this morning on CNN news with Dr. Phil (popular talk show host and a common sense, street smart individual) warns that people should be educating their children about quality eating habits so they can pass that knowledge and lifestyle on to future generations.

  5. Megan 12 November 2010 at 6:03 pm #

    I think that dentists rather than doctors are leading the way on the advantages of low-carb diets. They know that grains and sugars, not fats and proteins, rot teeth and gums; they know that the genetically altered to be high fructose fruits /fruit juices we consume for “health” are disastrous. Presumably the scientists who recommend a fat tax are the same ones telling us we need even higher doses of statins. I think it’s true that many researchers and arrogant consultants would rather risk our health than admit they’ve been barking up the wrong tree for decades.

  6. John Bowman 12 November 2010 at 9:23 pm #

    Why does anyone imagine this is about politicans caring about our health?

    1) The HM Government in its various political hues has got the Nation £4.8 trillion into debt. It needs the money so watch out next perhaps for a waistline tax.

    2) There will be a de facto 2.5% rise in the cost of fatty foods when VAT goes up to 20% as whilst fresh foods are zero rated, processed foods and snack foods are not. That will be an overall 5% increase since the last lot of loons reduced VAT to 15% what can only be a few months ago during what turned out to be a 13 year nightmare.

    Taxes on anything can only have a discouraging effect if they are high enough and increased well ahead of the rate of wage inflation. Such taxes would be unacceptable.

    In any case it raises the possibility that the target group will forgo other foodstuffs in favour of their fatty favourite.

    Petrol is a good example of ever increasing high taxation, yet increasingly more is used.

    The conclusion, as with so called green taxes, it is just another method of collecting tax under the guise of a worthy motive.

  7. Chris 15 November 2010 at 4:40 pm #

    I absolutely agree with you about fats. But isn’t it important to distinguish between simple and complex carbohydrates?

    What about sugar: isn’t that one of the worst culprits? What about a tax on sugar?

    It is little more than eighteeen months ago that a delegation of GPs narrowly voted against a proposal by Lanrkshire GP, Dr David Walker, to tax ‘chocolate’ in much the same way as alcohol and cigarettes. (BBC online news item.)

    I spoke to David not long after the story. He’s a well intentioned GP and additionally qualified in nutrition. I respect his opinion but question his prescription. I agree that chocolate confections being high in sugar and denatured vegetable oils may well have consequence in the proliferation of obesity and certain chronic disease. However I have reservations about taxing them.

    One reservation is that the least fortunate in society seem to be the ones that persist with consumption even in the face of additional duty being levied upon such items. The other is an observation that corporation tax upon the large and profitable concerns that make such stuff and market it with such enthusiasm shows a long term trend of falling as a proportion of overall taxation.

    We find ourselves living in a complicated world mostly of humanitys’own making in which the vulnerable are, for want of an alernative word, vulnerable to exploitation.

    It is not just in medecine that there seems a willingness to treat symptom as a preference to establish and eradicating cause.

    Complex carbohydrates are not so distinguishable from sugar. Raw they are not so digestible. But cooked they exhibit properties such as GI an GL that fairly closely approximate to glucose.

  8. Jill H 15 November 2010 at 9:07 pm #

    Processed foods are designed, many believe, to make you want to eat more. Sugar, altered and damaged fats that the body cannot recognise and therefore do not sate the appetite, salt and sophisticated additives:- emulsifiers, stabilizers, firmers, gellers, aerators, anti-cakers, improvers, thickeners, thinners, binders and buffers, ‘cosmetic’ flavors and colors. Michael Pollen calls this stuff ‘edible food-like substances’. Should there be effective pressure on food manufacturers for stricter regulations on ‘processed’ foods in the public (our children’s) interests? I don’t know. But I absolutely agree with what Stephen has already said. Reconnection to cultural identities. For most of our history what we have chosen to eat has been handed down from grandmother to mother, father, children. Scientists seem to have taken over from mums and we need to gain the knowledge back to feed children ‘real’ food.
    I think there is a lot of confusion when talking about ‘complex’ and ‘simple’ carbohydrates (at least I feel confused). Complex carbohydrates I think of as foods such as vegetables and fruits (as well as grains) and just not in the same camp nutritionally as ‘simple’ i.e. processed carbs found in manufactured food.

  9. Justmeint 17 November 2010 at 12:43 pm #

    As with all forms of taxation – they really will not benefit YOU the taxpayer.

    You will no doubt be familiar with a pending Carbon Tax which Greenies and Governments around the world, want to impose on consumers, ostensibly so that we will reduce the amount of carbon we use – in everyday life – such as in gas emissions, electricity usage, heating and cooling around our homes and offices etc etc etc. All the aforementioned will of course, save us and planet Earth from the inevitable destruction, which they tell us, carbon causes.

    Are you aware that a small isolated community, 1000km off the coast of Australia is to be trialing a Personal Carbon Credit Scheme? It will also involve a food tax/fat/tax scheme as well.

  10. John Walker 2 January 2011 at 2:14 pm #

    Any ‘food-tax’, ‘waistline-tax’ or whatever, will be levied according to out of date data…

    E.g. the BMI.
    A healthy, active short person who has a good muscle-mass could easily show a high BMI. This means the dogmatic, BMI conscious professional will deduce, incorrectly, that such a person is obese!

    I fear the myths are far to entrenched now to get anything changed. The struggle I am having with my wife, who wants me to ‘cut down on meat and fats’ is an example. I just cannot get her to see the evidence.

    It’s down to us individuals to decide for ourselves.

    So I cut down on bread and spuds and the beer! And any time I hear anyone espousing the idea of fat being fattening, I just lean over and say. ‘Read Dr. Briffa! If you don’t know who that is, Google his name!’
    I am looking forward to the time when I can pat a flat stomach and say, ‘Here’s to protein!’

    Happy New Year folks!


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