{"id":3233,"date":"2014-09-08T11:51:45","date_gmt":"2014-09-08T10:51:45","guid":{"rendered":"https:\/\/www.zoeharcombe.com\/?p=3233"},"modified":"2016-08-21T11:45:08","modified_gmt":"2016-08-21T10:45:08","slug":"the-low-carb-vs-low-fat-study","status":"publish","type":"post","link":"https:\/\/www.zoeharcombe.com\/2014\/09\/the-low-carb-vs-low-fat-study\/","title":{"rendered":"The low-carb vs low-fat study"},"content":{"rendered":"
On September 2nd 2014 a story broke in the field of diet and nutrition, but it barely made it across the pond. The New York Times headline was “A call for a low carb diet that embraces fa<\/a>t.” The Huffington Post covered the story, but didn’t devote a whole article to it. Instead they combined the findings of this study with another to report “What can we really<\/em> learn from that low-fat vs. low-carb study<\/a>?”<\/p>\n The BBC ignored it. The Mail did an on-line only piece “Time to throw out the bread<\/a>! A low-carb diet IS the most effective way to lose weight – and it cuts the risk of heart disease, too.” Great headline, but you wouldn’t have come across the article by chance. I had to do a very specific search on the mail site to see if they had covered it. Similarly the Guardian had an on-line story “Low-Carbohydrate Diet Protects Against Heart Disease Study Shows<\/a>.”<\/p>\n The study<\/strong><\/p>\n This is the link to the original article “Effects of low-carbohydrate and low-fat diets<\/a>.” Dr Michael Eades has very kindly dropped it in his box <\/a>for you to be able to see the full article.<\/p>\n Start, as usual, with any conflicts of interest. The study was funded by the National Institutes of Health, which is very interesting in itself. It’s the first study I’ve seen funded by a public body to review the effect of low-carb diets, let alone as compared to low-fat diets – the latter typifying public health advice. There is a full conflict of interest form<\/a>, covering all authors involved in the study here. It is unusually and refreshingly completely void of any conflicts whatsoever. Oh to find a drug or food item study so genuinely independent.<\/p>\n The study was simple in design and meticulous in execution. Many of the medical site reviews of the study <\/a>detailed and\/or complimented the care that had been taken to make the trial as controlled as possible.<\/p>\n The study involved 148 men and women without cardiovascular disease or diabetes. The men and women were aged 22 to 75 years and had a BMI of between 30 and 45, so that they had sufficient weight to lose over the study period. The participants were recruited from the general public through open adverts. This generated more response from females than males, resulting in 89% of the subjects being female. The study was undertaken in New Orleans, Louisiana. 51% of the participants were black, 45% were white and the remainder were Asian and Hispanic.<\/p>\n 73 of the participants were randomly allocated to the low-fat diet and 75 were randomly allocated to the low-carb diet. Table 1 in the paper shows the baseline characteristics of the participants. This is where we can check that the randomisation ‘has worked’ and we are equally like to have similar numbers of females in each diet group, similar numbers of different ethnic origins, similar starting weights and so on. The low-fat group were a couple of years older than the low-carb group and they were 1.6kg heavier on average (i.e. more weight to lose), but, Table 1 overall is reassuring that the groups started off from a very similar baseline.<\/p>\n The diet<\/strong><\/p>\n The study noted that there have been very few attempts to study low-carbohydrate diets and none had ticked two important criteria of 1) actually being a low-carb diet and 2) studying a diverse population. The Gary Foster (2003) study <\/a>did compare an actual low-carb diet (Atkins) to a low-fat (government advice) diet, but this did not involve a diverse\/carefully randomised population. This study, covered in the BBC Horizon programme about The Atkins Diet, concluded that Atkins was better for weight loss and cholesterol measures. The usual attempt to study a ‘low-carb’ diet has involved carb intake in the 100-200g range. That’s a high-carb diet to the low-carb world!<\/p>\n This was different. The low-carb diet group target<\/em> was less than 40g of carbohydrate a day. The low-fat diet group target<\/em> was less than 30% of daily energy intake from total fat and less than 7% from saturated fat – model government advice therefore. I emphasised the word target because the discussions on-line about the study didn’t pick up the actual intake reported in the paper.<\/p>\n Table 2 reported the actual intakes of carbohydrate and fat for the two groups:<\/p>\n The low-carb group were supposed to consume <40g carb per day. They did in fact consume, on average: 97g carbohydrate\/day at 3 months; 93g\/day at 6 months and 127g\/day at 12 months. The low-carb group thus substantially missed their targets.<\/span><\/p>\n The low-fat group, in contrast, did hit their total fat targets (they recorded saturated fat intake of between 8-9% during the study). They were supposed to consume less than 30% of their daily intake from fat and they achieved this: 27.5% at 3 months; 27.9% at 6 months and 29.8% at 12 months.<\/p>\n The researchers reported that 5 people dropped out of the low-fat group and 5 people dropped out of the low-carb group after 3 months. By the end of the study (at 12 months), 13 people in total had dropped out of the low-fat group and 15 had dropped out of the low-carb group. That was an 18% drop out in the low-fat group and a 20% drop out in the low-carb group. That’s a reasonably low drop out rate for a diet study and a number dropped out due to life stressors and\/or pregnancy – understandable with a largely female group 22 years old and above.<\/p>\n The results<\/strong><\/p>\n The results fell into two main areas: weight and what the researchers called “cardiovascular risk factors.” One of these I value (weight), the other I don’t (cardiovascular risk factors – apart from to wave at people who do value it).<\/p>\n Weight<\/strong>: To quote verbatim from the study: “Weight loss was greater in the low-carbohydrate group than in the low-fat group at 3, 6, and 12 months.”<\/p>\n The main results are worth capturing in a little table (this is an extract from Table 3 in the paper).<\/p>\n