The Michael Mosley August 2012 Horizon programme started a significant interest in intermittent fasting. As my special report (free) explains here, the programme looked at a number of different restricted eating options (eating less all the time, fasting for 4 days, alternate day fasting). The option that Mosley found the most tolerable was eating ‘normally’ for 5 days and eating one quarter of ‘normal’ calorie intake for 2 days. Thus the 5:2 concept was launched on the British population and a number of copy cat books appeared even before Mosley’s own 5:2 book was published, as “The Fast Diet” in January 2013.
Another 5:2 diet was being researched before the Horizon programme. Michelle Harvie was the lead author on a paper published in the International Journal of Obesity in May 2011. The full article is available here .
This blog was posted on 22nd April 2013. I received an email from Michelle Harvie on 24th April requesting some amends. We have had a few email exchanges since and any changes to the original blog are in red below.
The Intermittent Fasting Study
The study involved 107 women who were randomly assigned to either a Continuous Energy Restriction (CER) diet or an Intermittent Energy Restriction (IER) diet. To quote from the article: “The CER group were prescribed a daily 25% restriction based on a Mediterranean type diet (30% fat, 15% monounsaturated, 7% saturated fat, 7% polyunsaturated fatty acids, 45% low glycaemic load carbohydrate, and 25% protein). The IER group were asked to undertake a Very Low Calorie Diet (VLCD) (75% restriction) on 2 consecutive days and to consume estimated requirements for weight maintenance for the remaining 5 days according to the nutrient composition above.”
The Very Low Calorie Diet (VLCD) part of the intermittent group’s diet provided approximately 500 calories per day. It was low carb as well as low calorie – delivered in the form of 2 pints of semi-skimmed milk, approximately 300g of vegetables, 1 portion of fruit, a salty low calorie drink (why?!) and a multivitamin and mineral supplement.
Participants in both groups were advised to maintain their current activity levels throughout the trial, and did not receive specific exercise counselling. Energy prescriptions were reviewed throughout the trial to account for changes in weight and exercise levels to maintain a 25% restriction below estimated requirements for weight maintenance.
If we assume that an average woman in each group needed 2,000 calories a day and assume for simplicity that this did not change during the trial, then the average woman in the CER group would need 14,000 calories per week and would receive 10,500 – a sustained reduction of 25% per day. The average woman in the IER group would need 14,000 calories per week and would receive 11,000 – a reduction of 1,500 calories on 2 days. Thus the weekly calorie intake and deficit would be essentially the same. (Notwithstanding everything I write about the type of calories being far more important than the number).
107 women started the 6 month study. 18 women withdrew from the study before completing the 6 months: 11 from the intermittent group and 7 from the continual restriction group. Did the starve-for-2-days group find the diet more unbearable therefore?
Here is the passage reporting the results verbatim from the study:
“Weight loss was comparable between the groups. LOCF [Last Observation Carried Forward] analysis at 6 months showed weight reduced from mean (95% CI) 81.5 (77.5 to 85.4) kg to 75 (71.2 to 78.8) kg in the IER group compared to a reduction from 84.4 (79.7 to 89.1) kg to 78.7 (74.2 to 83.2) kg in the CER group. The percentage of women in the IER and CER groups losing 5–10% body weight were 30 and 33% respectively, and losing 10% or more body weight were 34 and 22% respectively (χ2=1.89, P=0.39). Both groups experienced comparable reductions in body fat, FFM [Fat Free Mass], hip, bust and thigh circumference and composition of weight loss. Percentage of weight lost which was fat in the IER and CER groups was 79 (±24) and 79 (±26) % respectively (P=0.99).”
Removing the statistical details for ease of observation, the above passage tells us:
– “Weight loss was comparable between the groups.”
– “Both groups experienced comparable reductions in body fat…”
– At 6 months, the IER (intermittent) group had reduced on average from 81.5kg to 75kg. The CER (continuous) group had reduced on average from 84.4 to 78.7kg. Both groups lost approximately 6kg on average, equating to approximately a 7-8% reduction from starting weight.
– That’s 1 kg a month. That’s 2lb a month. Hardly justifying the Daily Mail headlines “The diet revolution that’s swept Britain.” If I starved for 2 days a week and never ate more than normal on the other 5 days, or cut back 25% every single day for 6 months, I would want significantly more than a 0.5lb a week weight loss. The record weight loss for The Harcombe Diet (Phase 1) is 17lb in 5 days. I would be astonished if someone didn’t lose more in 5 days of Phase 1 than in 2-3 months of the average on this diet and with far fewer rules and restrictions.
As Dr. Margaret McCartney noted in this clip from Radio 4’s Inside Health (listen from approximately 20 minutes into the programme) – the clinical trial “didn’t show any difference.” Quite so.
Despite the poor results in this clinical trial, the diet has been published in a book called “The 2 day diet”. (This last sentence was wrong – as you will see below – this 2011 article was not the diet in Harvie’s book). It was serialised in the Daily Mail from the 11th February 2013 onwards for a week. These articles are not available on line (to make you buy the paper and/or the book). Another serialisation started in the Daily Mail on Saturday 20th April – again – the details of the diet are not available on line.
Harvie states “The most important point is that our 2 day diet book is not based on the original milk and fruit and vegetables (650 kcal) diet which was reported in the Int J obesity in 2011. This was a proof of principle study showing that 2 day diets could work.”
This was most enlightening, as it discounts the 2011 study as being able to play any part in the “clinically proved” claim of the 2 day diet in the book. I’ve left the study in this blog, for interest, (not least to show how poor the weight loss is), but it plays no part in claimed clinical proof.
Harvie goes on to say “The book is based on our improved low carb 2 day diet, and the statistics used to support the weight loss reported in the book have come from our recent publication in the British Journal of Nutrition.” (BJN henceforth)
I have had an email exchange with Harvie challenging the claim that the diet in the BJN is the 2 day diet in her book. She stands by the claim and states “The diet in the book is the diet inn (sic) the aper (sic). The diet showed significant reductions in fat which is what we claim for the book.”
However, I cannot see the evidence for this (I have a copy of the full paper). The paper compares three diets – two involving what is called “Intermittent Energy and Carbohydrate Restriction” (IECR) (my emphasis) and one involving “Daily Energy Restriction”. The paper states “The IECR and DER interventions involved an overall 25% energy restriction… Participants randomised to IECR were asked to restrict energy and carbohydrate on two consecutive days each week (70% energy restriction and 40g carbohydrate) and to consume a euenergetic Mediterranean-type diet that met estimated energy requirements for the remaining 5d of the week. Restricted IECR days provided between 2500 and 2717kJ…”
2500-2717kJ is 597-649 calories. The intermittent diet reviewed in the BJN study was both calorie and carbohydrate restricted. Taking just the protein and fat servings for a woman in the restricted days of the 2 day diet (the diet is detailed below), and looking just at calories, a woman could have 12 medium eggs and 35 grams of olive oil (choosing just two foods to keep the analysis simple – the different foods allowed are unlikely to be significantly different in calories per serving size) and these alone (before the dairy, fruit, veg, mints) would add up to 1,065 calories. Indeed in another part of her correspondence Harvie says “The restricted days often end up self limiting to around 1000 kcal i.e. a 50% and not starving yourself.”
You can’t have it both ways. The diet in the book is not the diet in the paper. The diet in the book has not, therefore, been clinically proven.
Notwithstanding this, the BJN paper did not claim any significant difference in weight loss between the diets. “Both IECR groups experienced significantly greater and comparable reductions in body fat than the DER group, but no significantly greater reductions in weight.” Harvie makes no claims for weight advantage in her email to me when she states “The diet showed significant reductions in fat which is what we claim for the book.” However the back cover of the book states “Lose more weight and twice as much fat as on a standard calorie-controlled diet – then keep it off forever”. The last part is also unproven – a month’s maintenance followed the three month diet and a check at four months following baseline is the latest assessment recorded by the study. Significantly this is two months before the well-documented six month regain observed with calorie deficit diets.
Before you get excited about the fat claim – the intermittent dieters (having approximately 600 calories a day for 2 days a week remember) lost an average of 3.7kg of fat in 3 months. That’s just over a couple of pounds a month. A month – not a week.
We should also make the point that neither the 2011 nor the 2013 paper study men. Both study women. Hence there can be no claim that either intermittent diet reviewed by Harvie/Howell has been clinically proven for men, notwithstanding that the diets for women in the journal articles were different in both cases and neither the same as the one in the book.
The book authors are Michelle Harvie – a dietician and Tony Howell – Professor of Oncology. Together they run Manchester University’s Genesis Breast Cancer Prevention Centre.
The front cover of the book has the words “clinically proven.” The Daily Mail February serialisation majored on the claim “clinically proven to reduce weight.” The “clinically proven” refers to the article in the International Journal of Obesity. Despite the fact that weight loss overall was low and there was no difference between the intermittent diet and the continuous calorie deficit diet, because this was done as a study the authors are able to make the “clinically proven” claim. (As per the probably unintentionally helpful intervention from Harvie above – I can see no evidence that any clinically proven claim can be made.)
“Clinically proven to lose you an average of a couple of pounds a month over 6 months” would be more accurate. “Clinically proven to do no better than normal dieting” would have been another option.
Stopping at 6 months is also interesting as all evidence from Keys (1945) to Franz (2007) to Weight Watchers (2010) shows regain starting at approximately 6 months after starting a calorie deficit diet. The 5:2 diet has not been clinically proven to achieve sustained weight loss.
The Daily Mail got into misleading territory in the February serialisation. Here is a direct quotation from the article on 11th February 2013: “In a study of 34,000 women, Dr Harvie and Professor Howell were the first to discover that being overweight significantly increases your risk of breast cancer and that losing just 5 per cent of your body weight and keeping it off is enough to reduce your risk of breast cancer by a staggering 40 per cent.”
First, were Harvie and Howell really the first to discover that being overweight significantly increases the risk of breast cancer? Really? Here’s a study I found in a quick search dating back to 1993. Did Harvie and Howell produce a study before this?
Harvie says “For the record we weren’t the first group to report that being overweight significantly increases your risk of breast cancer, but were the first to report that losing just 5 per cent of your body weight and keeping it off is enough to reduce your risk of breast cancer by 25- 40 per cent within the Iowa Women’s Health Study”.
It is not an absolute truth that losing 5% of your body weight and keeping it off can reduce your risk of breast cancer by 25-40%. A study may have found an association, not causation, of a relative, not absolute, risk. If this is the study being referred to, there were 1,987 incidents in over 440,000 person years of follow up. That’s a 0.45% chance of an incident in any study year. That’s why I get annoyed when researchers dramatise/scare people with relative risk headlines. The absolute risk is difficult to even conceive.
Secondly, if the observation is that a 5% sustained weight loss reduces the risk (remember, this will be relative risk, not absolute) of breast cancer, then any diet that achieves weight loss could claim to reduce the risk of breast cancer. Here’s my suggested headline: “The Atkins diet reduces the risk of breast cancer.”
The Mail (Feb) continued “Their diet, which is clinically proven to be more effective than conventional dieting.” This is simply not true. The 2011 journal article stated quite clearly ” Weight loss was comparable between the groups.”
The Mosley 5:2 diet advises that the days should not be consecutive. The Harvie/Howell diet says that the 2 days should be consecutive. The Harvie/Howell diet claims that there is no calorie target on the 2 days – just foods that you can’t eat. You’re joking of course! There is a directive for fat to be eaten, carbs to be eaten and protein to be eaten – with portion sizes spelled out and these portion tables by macro nutrient are dictated for the ‘non-diet’ days as well as the ‘diet-days.’
The concept sounds simple enough” Spend two consecutive days each week enjoying protein (fish, meat, eggs) and vegetables but no carbs (potatoes, bread, pasta) and then stick to a ‘healthy Mediterranean-style diet’ for the other five days.”
This is the reality:
These are the numbers and sizes of the protein, fat and carb portions that you are allowed on DIET DAYS:
PROTEIN: a maximum of 12 servings for women and 14 servings for men.
1 portion = 30g/1oz oily fish; skinless chicken; lean beef, pork, lamb or offal.
1 rasher lean bacon; 1 egg
50g of tofu.
60g white fish.
45g/1.5oz of seafood/tuna in brine.
FAT: maximum of 5 servings for women and 6 servings for men.
1 portion = 8g margarine (avoid buttery types), 7g olive oil, 3 walnut halves or 8 peanuts, 8g peanut butter; 10 olives; 15g low-fat mayo.
DAIRY: Men & women 3 servings.
1 portion = 1/3 pint skimmed/semi-skimmed milk/soya milk; 3 tablespoons diet yoghurt; 2 tablespoons normal yoghurt; 30g/1oz reduced fat cheese.
FRUIT – Men & women 1 serving.
1 portion = 80g/2.5oz portion of low carb fruit (apricots, berries, rhubarb etc)
VEG/SALAD: 5 servings.
1 portion = 80g/2.5oz of low carb veg (green beans, asparagus, broccoli, cabbage etc).
TREATS – sugar free gum?! up to 10 sugar free mints!
DRINKS – At least 2 litres a day of water, tea, coffee or other sugar-free or low-calorie drinks.
This confirms that a dietician and a professor don’t know one macronutrient from another. Protein is in everything except sucrose (table sugar) and oils. All the foods listed under protein are combinations of fat and protein (fish, meat, eggs). Some of the ‘proteins’ contain carbs as well as protein and fat (lentils, beans).
Harvie asked me to correct for the fact that “we do not allow lentils, beans and baked beans on restricted days.” I am happy to correct this and have deleted those entries under the restricted days above.
Harvie states that she and Professor Howell “do know one macronutrient from another” and that the protein, fat and carb food lists represent the main ingredient of those foods.
Harvie and Howell may well know one macronutrient from another, but they don’t know the main macronutrient in lentils, beans and baked beans. 100g of boiled lentils has 0g fat, 9g protein and 20g carbohydrate. The remainder is water/ash. 100g of boiled beans has 0g fat, 9g protein and 23g carbohydrate. The remainer is water/ash. 100g of cooked baked beans has 0g fat, 5g protein and 20g carbohydrate. Carbohydrate is the main macronutrient in all three of these examples given.
Under fats, margarine and olive oil are fats. Nuts and avocado contain carbs, fat and protein in good measure. And what on earth are a dietician and a doctor doing advising hydrogenated (or interesterified), bleached, deodorised, emulsified, coloured and fortified margarine in preference to natural, nutritious butter? And what on earth are a dietician and a doctor doing advising low calorie, sweetened, drinks as part of a healthy diet. Have they not googled “the dangers of aspartame”?
(I was being a bit tongue in cheek here, as 99% of doctors and dieticians sadly promote interesterified, bleached, deodorised, emulsified, coloured and fortified margarine over natural, nutritious butter and don’t seem to know the harm that aspartame can inflict – Harvie and Howell are just no different). Harvie has asked me to point out “We have summarised the most up to date evidence based research on asparatame and saturated fat in the book, and not all the hype and anecdotes and personal viewpoints which may appear on Google.” The book has two paragraphs on sweeteners, covering aspartame among others. Of the many dangers associated with aspartame it lists one – blood cancer – and thus recommends limiting intake of diet drinks to no more than nine cans per week!
On saturated fat, there is no evidence that Harvie and Howell know that meat has more unsaturated than saturated fat. They make the common recommendation to cut down on meat to reduce saturated fat and to replace saturated fats with ‘healthy’ fats, especially monounsaturated fats. There is more unsaturated fat than saturated fat in meat (red, white, whatever) and the main single fat in meat is (with the odd rare exception) monounsaturated. The book also claims that “saturated fats clog arteries.” Ha ha – only if you intravenously inject them!
NON-DIET days (Puh-lease!)
“You are basically eating a healthy Mediterranean diet with lots of fresh fish, meat, salad, vegetables and whole grains” say the authors. Please see this blog for the never ending nonsense about the Mediterranean Diet.
These are your food allowances on non-diet days. How the heck is this not a diet?!
Men (max servings)
|15 stone +|
Women (max servings)
|14 stone +|
Serving sizes of protein and fat are as for the diet days.
The carb servings for the non-diet (ha ha) days are as follows. You are advised to “always choose wholegrain.”
1 portion = 3 tbsp whole wheat cereal; 1 weetabix; 1 heaped tbsp oats; 1 slice wholemeal bread; 1/2 roll; 2 rye crispbreads; 1 oatcake; 2 heaped tbsp cooked pasta; 1 lasagne sheet; 1 small potato; 2 tbsp sweet corn kernels.
The small print
“Do not do this diet as a child, teenager, pregnant, breastfeeding, suffering from an eating disorder. The high protein may post problems for those with kidney disease or at risk from kidney disease. Diabetics – seek advice.”
The final word
The Friday 15th April Daily Mail article described the diet as “It’s gloriously simple”!
I love maths, but I would lose the will to live even trying to work out one so-called non diet day of the triple simultaneous equation that would be my carb/fat/protein number and size of portions – even allowing for the fact that the diet doesn’t know fats from proteins or carbs.
This is a 7 day diet, delivering barely a quarter of the calorie intake needed on 2 days of the week. That’s 30% of your life starving and 100% of your life on a diet – counting portions and measuring out 80g of vegetables. (As noted above, Harvie states that “The restricted days often end up self limiting to around 1000 kcal i.e. a 50% and not starving yourself” – proof that this is not the approximately 600 calories intermittently in the BJN article).
Don’t do it!
This is obsessive and miserable and it’s proven to lose an average of 0.5lb a week – if you stick to the diet for 6 months. Then we don’t know if you will regain. I can confidently forecast that you will need to stay on this kind of restrained eating for life or you will regain – you will have trained your body to maintain on a lower calorie intake.
Or you could just eat real food (meat, fish, eggs, dairy, vegetables, fruits in season and whole grains in moderation); three times a day and get on with your life. But then that would be The Harcombe Diet!