Book review may signal change is in the air

A book review may not be a policy statement, but it may reveal some of the thinking and views of the reviewers. The review in question is that of Nina Teicholz's journalistic tome "Big Fat Surprise: Why Butter, Meat & Cheese Belong in a Healthy Diet" which explores and exposes the background and evolution of current dietary guidelines. Nina herself halved her blood triglycerides by switching to a diet of "60% fat (plenty of it saturated), 25% protein and 15% carbohydrates" however it should be noted that she is an investigative writer rather than a research scientist or n=1 experimenter.

The authors of the review are Debbie Cook and David Haslam of the UK's "National Obesity Forum" - "Debbie Cook is the Vice Chair at National Obesity Forum, and a Nurse Practitioner and Clinical Nurse Manager" and Prof David Haslam is the Chair of the National Obesity Forum and  the eminent non-executive Chair of the UK's National Institute for Health and Care Excellence (NICE).

It seems likely, or at least possible, that the review will disappear in a storm of controversy, but some of the interesting extracts are :-

The UK is ready for the revelation that sugar is toxic, and that refined carbohydrates and fruit juice are detrimental to health, and has taken it fairly well. But the next big shock wave – that another macronutrient is an important, healthy and necessary part of the diet: namely saturated fat – may take some swallowing. 

 In a meticulously well researched book, we are informed and educated about why the modern world faces an epidemic of obesity, why generations of Americans religiously followed the nutritional dogma fed to them by researchers of questionable integrity.

Does low fat diet give faster fat loss than low carb ?

A recent Poster presentation (ie not fully peer reviewed published science) posed the question

"Is a Calorie a Calorie? Metabolic Fat Balance Following Selective Isocaloric Restriction of Dietary Carbohydrate Vs. Fat in Obese Adults. - Kevin D Hall et al.

and went on to describe a clinical study where about 800 calories of either fat or carbohydrate were removed from the diet of the same group of subjects in a crossover design. So the grams of protein stayed the same, and in the low fat arm the grams of carbohydrate stayed the same with the fat remaining constant in the low carb arm.

This is quite a good design, as it saves protein changes having an effect. It does constrain the low carb arm to a relatively high carbohydrate content (30%) because the caloric reduction takes the fat in the low fat arm down to only 7% or 15 grams a day.

From the limited data in the abstract I have tried to calculate the average intakes :-

	Baseline	Low Carb	Low Fat
Calories/day (kcal)	2720	1930	1920
Carb energy %	50	30	72
Fat energy %	35	49	7
Protein energy %	15	21	21
C grams	340	145	346
F grams	106	105	15
P grams	102	101	101

During the experiment the subjects spent time in a metabolic chamber where gas analysis, temperatures and airflow measurement allows calculation of their metabolic rate and the proportion of their energy supplied by fat and carbohydrate. The authors used this data to calculate the fat loss based entirely on "fat exhaled" rather than traditional weighing and body composition analysis.

After 5 days on the baseline diet the subjects were allocated to either Low Carb or Low Fat for 6 days, then returned after two weeks to repeat the baseline diet and the opposite arm of the calorie reduction. Weight loss was greater on low carb than low fat, 1.9±0.2 vs. 1.3±0.1 kg; p=0.05. That's more than a pound greater in less than 6 days, this is often seen as the initial weight loss of water due to carbohydrate restriction and its diuretic effect.

Despite the greater weight loss on low carb, the authors report that "body fat loss was ~67% greater after 6 days of LF vs. LC (394±40 vs. 236±30 g; p=0.0003)." At 9 cals/g that equates to 591 cals/day on LF and 354 cals/day on LC. To try and understand why, and where the apparent energy imbalance occurs, we need to calculate the oxidation rates ( "burning" ) of carbs and fat. We'll do this by assuming that the food being eaten is oxidised at the same rate and that additional energy is supplied from body reserves :-

Calories expended	2720
Change in cal exp	reported	-72	-81
Extra fat burn cals		426	-53
Extra fat burn grams		47	-6
Fat Oxidation grams	106	153	100
Fat Balance in – out	0	-48	-85
Difference LC – LF		37
Total body fat loss g	reported	236	394
Per day grams	5	47	79
Extra LF vs LC			67%
Calories expended	2720	2648	2639
From fat kcal	952	1378	899
From protein kcal	408	405	403
From carbs kcal	1360	579	1382
Accounted for kcal	2720	2362	2685
Discrepancy kcal	0	286	-46
as fat grams		32
as carbs grams		71

The two diets both saw a small but similar calorie expenditure reduction from baseline of 72 and 81 calories a day. Fat oxidation increased significantly on the low carb diet giving 50% more fat burn but the extra 47 grams/day is less than the 90 grams a day taken out of the low fat diet.

Adding up the oxidised fat, protein and assuming that the carbs eaten were oxidised gives the "Accounted for kcal" row above, as the paper didn't report carbohydrate oxidation rate. There's a shortfall of 286 calories/day in the low carb case as not enough fat is being burned to provide the measured energy output. 

Without access to more data the best explanation I can offer is that the discrepancy was supplied by about 70 grams of carbohydrate oxidation from glycogen reserves - a transient resource that would not have lasted many days at this rate. Had the experiment continued for another week then glycogen would have dropped to a new equilibrium and either fat oxidation would ramp up or some other metabolic adaptation would occur (using less energy).

On the high carb diet the glycogen reserves remain topped up by carbohydrate intake and, perhaps surprisingly, the elevated carb intake and consequent insulin levels doesn't suppress fat release to the point where it can't keep up with energy demand.

The study could perhaps be improved by doing a 2 week run-in on the test diet before the 6 days under closer observation. This would make the observed days more representative of a steady state. 

Better results from low carb than lower fat.

 There's a lot of chatter over the pond and on t'internet about a recent study comparing low carbohydrate diet advice with reduced fat.

The work was led by Drs Bazanno and Hu of Tulane University, New Orleans and funded by the US National Institutes of Health. Its stated objective was

to examine the long-term effects of a diet low in carbohydrates, as compared to one low in fat, on cardiovascular disease risk factors, including blood pressure (BP), body weight and composition, serum lipids, plasma glucose, insulin, adipocytokines (adiponectin, leptin, resistin), and C-reactive protein (CRP) among obese adults.

Fruit vs Fruit Juice

As a low carb person I eat berries and sometimes an apple, but fruit juice to me is just a sugar solution. Fruit itself seems to be universally regarded as A Good Thing (TM) and although Robert Lustig has said "the vehicle is irrelevant" when talking about fructose, and admits that he doesn't want to be the guy to say fruit is bad, the reliance on fibre as a moderator is somewhat optimistic.

Overfeeding and weight loss on oil

Over 40 years ago a paper presented two studies on overfeeding with a high fat diet. I was drawn to read this by wanting to see how it compared with Sam Feltham's experiments and to address the general question about overeating on a low carb diet.

The paper is by German authors - Kasper, Thiel and Ehl - and may have suffered a little in translation as the two separate studies are somewhat intertwined. Well, here goes -

All calories are not equal

I was recently drawn to read a report of a clinical trial of over-feeding, conducted by Bray et al of Pennington Biomedical Research Center. This was an inpatient study looking at the effect of protein on weight gain in people eating 40% more calories than required for maintenance of body weight.

This study was brought to my attention as evidence that the number of calories is more important than the composition of those calories, and it was said that "all the extra calories were from fat". On further examination I found that it actually shows something different.

Atkins and 5 / 7 a day

Bit off fuss in the news this morning where a new study (statistical analysis) suggests that 7 a day "portions" of "fruit and veg" is better than the currently recommended 5 a day based on general mortality as well as death from cancer, heart disease and stroke.

In other words if you eat more vegetables and fruit you're less likely to die in a car accident. This may seem flippant but a) it is April 1st and b) that's what they're saying when looking at "all cause mortality"....

Death risk from any cause decreased as fruit and veg consumption increased. Risk of death by any cause was reduced by:

14% by eating one to three portions of fruit or veg per day

29% for three to five

36% for five to seven

42% for seven or more

Fresh vegetables had the strongest protective effect, followed by salad and then fruit.

Fruit juice conferred no benefit, while canned fruit appeared to increase the risk of death - possibly because it is stored in sugary syrup, say the researchers.

Let's not forget that " Potatoes and cassava don't count because they mainly contribute starch to the diet " - not that low carb eaters would be bothering with those things anyway.

So where does this leave the health concious low carb eater ? The good old 42 year old fad that is the Atkins diet usually catches some stick on these occasions, but let's remind ourselves of the facts that in Phase 1, the most restrictive, the current Atkins plan requires 12 to 15 grams of carbohydrate from foundation vegetables.

So is the Atkins diet compatible with 5-a-day or 7-a-day of vegetables (and fruit) ?

According to conventional wisdom dietitians a portion is 80 grams which I think originates from the World Health Organisation. 5 or 7 a day at 80 grams each is 400 to 560 grams a day. If the carbohydrate content is low enough, less than 5 grams per 100 grams of veg, then the limits of Atkins Phase 1 are not incompatible with 5 or even 7 a day :-

	Grams / day of vegetables
Carbohydrate g/day	400	560
12	3.0	2.1
15	3.8	2.7
	Carbs g/100g

[ Note for Americans - UK / EU labelling reports carbohydrates separately to fibre, effectively "net carbs", so these numbers are lower than you are used to. ]

Some example vegetables from Tesco.com :-

	Carbs g/100g
Green beans	3.2
Brussel sprouts	4.1
Cauliflower	3.0
Savoy cabbage	4.1
Spinach	1.6
Kale	1.4
Mushroom	0.4
Romaine lettuce	1.7
Asparagus	2.0
Broccoli	1.8

Clearly it is possible to comply with 5-a-day of vegetables and 7-a-day too if you're careful to pick the right vegetables.  You may be able to add 80 grams of raspberries a day (3.7g of carbs) into your discretionary non-foundation veg carbs too, or as you move into Phase 2 the chocie of vegetables and berries will increase accordingly.

I conclude that the Atkins diet is entirely compatible with the "5 a day" message, in fact it's effectively built in with the 12-15g of carbs from foundation vegetables. Enjoy !


PS Full study behind the headlines is "Fruit and vegetable consumption and all-cause,
cancer and CVD mortality: analysis of Health Survey for England data" by
Oyinlola Oyebode, Vanessa Gordon-Dseagu, Alice Walker, Jennifer S Mindell.
To be found online, currently with Open Access.
JECH Online First, published on March 31, 2014 as 10.1136/jech-2013-203500


PPS You might be interested in an audio podcast about getting overweight children to eat more vegetables (and fruit).