While some doubt the benefits of controlling carbohydrate intake, the fact of the matter is that there is now abundant scientific evidence that this approach is generally effective for the purposes of weight loss, while at the same time helping to improve biochemical markers of chronic disease such as blood sugar levels and levels of blood fats such as triglycerides.
In a recent study presented at the American Diabetes Association symposium held in Chicago recently, the effects of low-carb eating were compared to a diet restricted in calories and fat in a group of elderly obese individuals suffering from type 2 diabetes [1]. The study lasted for a total of 6 months. At the end of this, the low-carbers had lost an average of 6.83 kg in weight, compared to an average of 5.16 kg in the low fat group. This difference was statistically significant.
In addition, though, those restricting carbohydrate saw decreases in their triglyceride and blood sugar (glucose) levels that were, again, statistically significant compared to the low-fat eaters.
There are sound biochemical reasons why they offer potential not just for weight loss, but other health benefits too. Key to understanding how this can be relates to the fact that many starchy carbohydrates cause quite brisk and sustained release of sugar into the bloodstream. The extent to which a food disrupts blood sugar is expressed as its glycaemic index (GI). In the World of the GI, glucose (a very fast releasing food indeed) is ascribed a value of 100. Compared to this, French bread, baked potatoes, wholemeal bread, cous cous and cornflakes have GIs of 95, 85, 70, 65 and 81 respectively.
The sky-rocketing blood sugar levels starchy carbohydrates tend to invoke will induce the pancreas to secrete copious quantities of insulin – the hormone chiefly responsible for tempering sugar levels in the bloodstream. Yet, while essential to life, insulin has the capacity to stimulate the production of fat within the body, and can also inhibit of the breakdown of fat too.
Of course the problem with many of the starchy carbs is not just their inherent tendency to disrupt the body’s biochemistry, but also that we so often eat so much of them. Scientists have begun to account for the quantity of food typically consumed by measuring what is known as its ‘glycaemic load’ (GL). Simply put, this is calculated by multiplying a food’s GI by the amount of carbohydrate to be found in a standard portion of that food. The GL therefore gives a better guide that just the GI with regard to the tendency for a food to disrupt sugar and insulin levels. Not surprisingly, bearing in mind their prominence in the diet, most starchy carbohydrates turn out to have not just high GIs, but high GLs too. Their ability to cause gluts of insulin mean that while starchy staples we are encouraged to have our fill of may not be fatty, they nonetheless have considerable capacity to be fattening.
Bearing all this in mind, it should come as no surprise that low-carb diets can be effective for those seeking to lose weight. But how do such diets compare with the more conventional low-fat approach endorsed by many doctors and dieticians? To date, six trials (included the one discussed above) have pitted low-carbohydrate against higher-carb/lower-fat regimes over the medium to long term. All six of these studies found that weight loss after 6 months was significantly greater in the low-carbohydrate group than in the low-fat group. Three of these studies lasted for a year, at which point there was no significant difference in results. However, in one of these studies the individuals failed to restrict carbohydrate intake to the extent advised, and in the other dietary compliance was not checked at all. Because of these limitations, these studies cannot be used to judge the true effectiveness of low-carb eating in the long term. In the final year-long study, carb restriction (Atkins’ diet) resulted in about twice the weight loss of lower fat regimes (Ornish and LEARN diets) [2].
In one review, the effects of several lower and higher carbohydrate diets were compared [3]. Overall, lower carbohydrate diets were found to bring about an average weight loss of 12.4 kg, compared with just 3.4 kg on the higher carbohydrate regimes.
References:
1. Radulian G, et al. The effects of low carbohydrate diet as compared with a low fat diet in elderly patients with type 2 diabetes.
2. Gardner CD, et al. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: the A TO Z Weight Loss Study: a randomized trial. JAMA. 2007 Mar 7;297(9):969-77.
3. Bravata DM, et al. Efficacy and safety of low-carbohydrate diets a systematic review. JAMA 2003;289(14):1837-1850
thought you may be interested in this research. I think that if you decrease carb levels to minimal amounts you have to eat larger quantities of protein to provide anough energy. Something has to give – perhaps bowel problems – constipation has been reported to me by some atkins dieters. This is quite interesting!
Low carbohydrate dieters can eat larger amounts of meat
Low-carbohydrate diets may increase the risk of people suffering bowel cancer, scientists have claimed.
Researchers from Aberdeen’s Rowett Research Institute believe there is a link between eating less carbohydrate and reducing cancer-fighting bacteria.
The Rowett study saw 19 overweight men given three diets containing different levels of carbohydrate.
Low-carbohydrate diets, such as Atkins, have their critics, however supporters say studies have shown effectiveness.
In the long run, it is possible that such diets could contribute to colorectal cancer
Prof Harry Flint
Rowett Research Institute
The researchers said they had discovered a link between consuming carbohydrate and the production of a fatty acid in the gut that protects against colorectal cancer.
The acid, called butyrate, is produced by bacteria and helps kill off cancerous cells.
The researchers said they found low-carbohydrate regimes could cause a four-fold reduction in the cancer-fighting bacteria.
The diets start by reducing carbohydrate intake, including foods such as potatoes and bread.
The researchers said the danger comes if dieters are tempted to keep the level low.
‘Preventable disease’
They said the study showed a low carbohydrate group consuming only 24g a day – behind the high intake group at 400g – saw a four-fold drop in the level of the cancer-fighting bacteria.
Prof Harry Flint, who led the research, said: “In the long run, it is possible that such diets could contribute to colorectal cancer.
“It is a preventable disease, and there is evidence that poor diet can increase your risk.”
He said it was likely the results would be the same in women.
Professor Annie Anderson, Dundee-based nutritional adviser to Bowel Cancer UK, said: “Compared to other low fat diets, there is little merit in low carbohydrate diets, apart for the fact that that they can help people to lose weight.
“There are no long term benefits to cutting down on fruits and fibre, for example, in bread, and as this report shows, doing so is likely to have a negative impact on your bowel health and may increase your risk of bowel cancer.”
Chris – I’m planning to make the study you cite above the focus of tomorrow’s blog.
good – I have a question for you – I am intriqued by your book comments that people were bigger 10,000 years ago – where have you got that from. And if people were healthier eating unprocessed foods over a 100 years ago were they not eating bread and potatoes – so where does your argument stand for being a hunter gatherer? Please answer this as I cannot marry the two together
Chris – the evidence for the decline in height that coincided with the introduction of grain in the diet is clearly cited in the book. See the references at the back of the book that correspond to the citation numbers in the relevant chapter (chapter 3) for more information.
So, if there is evidence that health declined when we moved from a hunter-gatherer existence to a more ‘agrarian’ existence, does it not follow that a ‘hunter-gatherer’ diet may be better for us?
And subsequent chapters (if you have read them) provide the evidence that the same, broadly speaking, is true today.
I’m having difficulty understanding, quite frankly, how anyone could NOT understand the fundamental principle on which my book is based.
well I think you contadict yourself – and how do you account for the increase in height now. This so called primal diet is based on alot of guess work unless you know otherwise – how do you know that people were not milking animals – we do not know. I will read the book because I think it is important to see what is around but I am totally unconvinced. As u say in the book whenpeople were eating unprocessed food over 100 years ago they were healthier. I think most of our health problems are post war with our overreliance on poor convenience junk. When I was a child in the 60s and 70s no kids were over wt because we ate real food and walked everywhere. It is too simlistic to just blame dread and milk! Ans me onething – do you ever eat them or have alcohol.
Chris
“well I think you contadict yourself – and how do you account for the increase in height now.”
My suspicion is that the increase in height is related to generally greater food intake (not better food).
“This so called primal diet is based on alot of guess work unless you know otherwise – how do you know that people were not milking animals – we do not know.”
Well, I’ve referenced the evidence for the likely time of introduction of dairy products in my book. You can ignore it if you want, but it is in there.
“I will read the book because I think it is important to see what is around but I am totally unconvinced. As u say in the book whenpeople were eating unprocessed food over 100 years ago they were healthier.”
Please can you point me to where in the book I make that claim?
“I think most of our health problems are post war with our overreliance on poor convenience junk. When I was a child in the 60s and 70s no kids were over wt because we ate real food and walked everywhere. It is too simlistic to just blame dread and milk! Ans me onething – do you ever eat them or have alcohol.”
Granted, the diet 50 years ago was almost certainly better than it is now, but that does not make it the ideal diet for us generally. Can you explain what relevance my own personal diet has in all this? Is it not enough to stick to common sense and science? Can I refer you back to the 300 plus references at the back of my book? Can I suggest you will find them far more enlightening than than knowing more about my own dietary habits.
well john I like to know u practise what u preach – I do!
I believe we are role models!
People give in and your diet is so restricted that I think most would.
Page 13 – bullet point 2!
Surely at that point in time people were eating bread and masses of potatoes to fill themselves up or they would starve.
If the diet was better 50 years ago why dont we go back to it – I was brought up on very old fashioned eating habits – i know the meat , 2 veg etc and I have actually done this with my own kids and they are lean fit and healthy.
ps i will finish the book – my husband is going mad that i will take it on hols!
Where in my book (or anywhere) have I decried meat and two veg as a meal? Actually, I often advocate it.
The bullet point you refer to itself refers to the robust health of
individuals eating a natural, unprocessed diet. NONE of these diets were found to be full of bread or potatoes (as you would well know if you had actually read the chapter).
In my view, there’s nothing particularly restrictive about the nutritional approaches advocated in my book. Please explain how you came to this conclusion. Or better still, actually read the book before posting any further comments about it.
i didnr say u said meat and 2 veg but any idiot would know that is what people ate then – actually probably more potato.
You are very good at cherry picking. I think there is no point in commenting u are just so wrapped up in this concept. I think that when I have finished wading thro the book I might come back but it is a dull and boring regimen that I suspect people cheat on .
As I asked you in another post, if I am cherry picking, please provide the orchard of evidence I am supposedly cherry picking from.
Oh, and do please bear in mind I don’t recommend too stringent an approach.
But then again, to know that you will have had to have read the book…
Why so defensive Chris, on something that you haven’t properly read yet?
I was brought up in the same era as you I was overweight
There is lots of information obout this floating around now,i’ve been sufferring with weak bones and general lack of energy.. When i looked at my diet i see nothing buy sugar laced rubbish.. too much white bread.. and too much dependance on the hits i get from sugars in my tea throughout the day.I’m changing my diet to avoid as much processed foods as possible.. i’d say it would be a hard life if you cut it out completely.. moderation is the key.. when you body is functioning really well.. it can handle the odd bit of junk.