by Jerome Burne
Medical and other health professionals dealing with diet and nutrition are keen to stress that their advice is firmly evidence based, backed up by properly conducted research. It’s the thinking behind the proposal to make Weight Watchers available on the NHS.
But an investigation by one of our contributors Zoe Harcombe has discovered that there is no evidence supporting the most fundamental principle behind the advice they have been giving for decades about weight loss.
In a post that has just gone up here, she describes in forensic detail what happened when she approached the seven top government and dietary organisations in the UK and asked them for the evidence supporting their claim that all you have to do to lose weight is to eat fewer calories than you expend in energy. Their response was almost unanimous: “We have no information on this.” For the full details of her personal survey see the link above.
Her question was based on an official leaflet from the BDA (British Dietetic Association) saying that: “One pound of fat contains 3,500 calories, so to lose 1lb a week you need a deficit of 500 calories a day”.
The theory that doesn’t make sense
Zoe was curious to know where this came from and what the evidence for it was. Intuitively it didn’t make sense, as it implied that she could cut back by 1,000 calories a day and weigh 6lb in a year’s time! Actually 6lb in less time than that, as 104lb of fat alone should have been lost – more on top in water.
So like one of those clear-eyed children whose questions can be hilarious and devastating to adult pretensions, she asked a number of them the same question: what was the rationale behind the statement about needing to have a deficit of 500 calories a day to lose 1lb a week?
The BDA replied: Unfortunately we do not hold information on the topic.” They suggested she contact a dietician. Already this was getting surreal – the members might know but the governing body didn’t.
Shortly after she attended an obesity conference that was full of dieticians discussing how to help people to lose weight but they blithely confessed they didn’t know either. One did say: “You’ve made us think how much we were just ‘told’ during our training, with no explanation.” This is a revealing glimpse of how this “science based” system is taught.
This should have been a disaster
Now this should have been a disaster for the whole dietician’s tribe. The mechanical plumbing model of weight loss – inflow must be less than outflow – is not some arcane technical point but the bedrock of all official weight loss advice.
Last month (May), for instance, NICE recommended that the NHS should pay for obese patients to go to 12 week commercial weight loss programs such as Weight Watchers. And what advice would they get?
This is from their website: “1lb of weight is equivalent to about 3,500 calories). Furthermore, reducing to 1,000 calories should result in a weight loss of 2lb per week and going down to 500 calories a day should result in a weight loss of 3lb per week? http://www.weightwatchers.co.uk/util/art/index_art.aspx?tabnum=1&art_id=29241
So what exactly happened when Zoe slogged round the august dietary bodies in search of an answer to her wide eyed question?
The National Obesity Forum (NOF) was no better informed than the BDA . their only response to her query was to try yet another body –the Association for the Sudy of Obesity (ASO). This was now firmly in pass-the-parcel territory. However the NOF did have one clarification to the calories in/out model and offered this explanation of how it worked: : “one less (sic) 50 calorie plain biscuit per day could help you lose 5lbs (2.3kg) in a year – and one extra biscuit means you could gain that in a year!”
The ASO also provided some more details of the theory showing the mathematical calculations that get you from the 50 calorie biscuit to five pounds a year and claimed that “this has been supported by numerous studies.” But when Zoe wrote again and asked for just one of them, she got no reply.
Next stop was NICE which mounted a slightly more robust defence quoting a study of just 12 people (12!) who had been put on a diet with a deficit of 600 calories a day. The result (and Zoe describes them rather more clearly than NICE did) was that after 12 months these twelve people had lost an average of 5kg (11 pounds) but the range was huge. One had lost just 0.32 kg (0.8 pounds) but another had lost 7.8kg (17.2 pounds.)
There are two glaring reasons why this provides no evidence for the calories in/out theory at all. First because the whole point of a formula like this is that it is precise. That is what the biscuit example tells us. One fewer biscuit a day equals 2.3 fewer kilograms in a year. Not 2kg fewer, not 3kg and certainly nothing about the possibility that some might lose 50x more than others.
No link at all between calories in and calories out
And secondly the average weight loss didn’t reach anything like the amount that the theory predicted from a deficit of 600 calories. Instead of 5kg it should have been 28kg. (Zoe’s article has all the workings on this)
The NICE data contained 15 more similar studies but none provided anything like evidence for the promised precise and consistent relationship between calories consumed and calories burnt. In all there was a wide range of results and the actual weight loss was far less than the theory predicted. In one case the gap between the amount that should have been lost and the amount that actually was, was 65 kilos.
By this stage of Zoe’s account of her simple search for truth I was totally convinced that this was a dead theory, one with a stake through its heart and shot with a silver bullet. But she is nothing if not dogged and thorough.
Two more organisations replied that they also could find no information. The Department of Health (DoH) said they were “unaware of the rationale for the formula” and NICE said: “we do not hold any information about the rationale behind the statement.”
Need for a fundamental review
Just one body DOM (Dieticians in Obesity Management) actually admitted the theory didn’t fit the facts: “I really think we need to fundamentally review the basis of current diet advice,” wrote the correspondent “and stop saying ‘to lose 1lb of fat you need to create a deficit of 3500 calories.”
What I haven’t made clear so far is that Zoe carried out this personal survey nearly five years ago and while it is shocking that the dieticians’ attempts to support one of their key theories was so feeble, what is far worse is that confronting them with this failure has resulted in absolutely no change in the advice they continue to give to the public.
In fact as the latest decision about Weightwatchers shows that dietary experts now plan to apply this zombie theory to thousands more patients at public expense. If the vociferous and aggressive sceptics lobby impartially applied their charge of “quack” to anyone selling non-evidence based treatments, they would have descended on the BDA, Nice, NHS and the rest and the rest long ago.
Time to abandom seriously flawed treatments
Zoe describes her feeling at the ability of these bodies to simply ignore this fundamental failing as: “incredulity that they still get away with spouting this nonsense.
“And daily incredulity that virtually all diet articles in magazines continue to repeat the lie: cut 500 cals a day and you will lose 1lb a week. I just can’t get my head around the fact that people can get away with this. That is what we are up against.”
If an “evidence based ‘ system is to mean anything it has to abandon treatments when they are shown to be seriously flawed and then investigate new ones. There is a lot of reputations and commercial interests riding on the current appraoch, the only people missing out seem to be the patients.