Sunday, September 27, 2009

Overfeeding humans: Jebb

"Obesity implies a failure of autoregulatory homeostatic responses to caloric excess"

The quote comes from this paper first authored by Mario Siervo but with Susan Jebb as the group leader. I'll discuss the paper in a moment.

Who is Susan Jebb?

From the Medical Research Council website:

Cross-government 2007- Chair, Expert Advisory Group on Obesity - Susan Jebb

Department of Health 2006 - Chair, Expert Group developing the Healthy Living Social Marketing Programme - Susan Jebb

Department of Health/Food Standards Agency 2004-2005 Expert Working Group on Nutrient Profiling - Susan Jebb

Government Office for Science 2006-2007 Science Advisor, Foresight Project 'Tackling Obesities: Future Choices' - Susan Jebb

You get the idea. An obesity politico. This sort of politico. Also check the date on that link. 2003. I was just starting on low carbohydrate eating at the time. Jebb was all over the papers. One very obvious thing, to someone who had just read Atkins' "New Diet Revolution" from cover to cover, was that none of the experts being quoted had read the book!

So that puts Jebb in context. Here's the interesting study on overfeeding humans rather than dogs. This is the feeding protocol:

3 weeks run in feeding
3 weeks 20% extra calories
1 week rest, eat as much of a Jebb diet as you feel like
3 weeks 40% extra calories
1 week rest
3 weeks 60% extra calories
3 weeks rest

This is the table detailing exactly what was eaten.

These are the weight changes, also subdivided in to tissue composition.

This is the executive summary: People got fat on the excess calories and couldn't loose the weight within 3 weeks. Some people couldn't loose any of the weight at all.

Jebb's conclusion. People pig out at Christmas and fail in their New Year diets. Greed and sloth, greed and sloth. Once you've pigged out, if you're greedy, you'll keep troughing.

Now, let's ignore Jebb and look what happened.

Protein was increased from 85g/d through 101g/d, 112g/d to 126g/d from baseline through over feeding protocol. Some increase, but not unreasonable.

Fat was used to increase the "energy density" of the diet and so was increased from 120g/d through 158g/d, 196g/d to 231g/d. The later being Kwasniewski levels for optimal health (but without the carbs!).

Carbs started at 322g/d and ramped up through 375g/d, 409g/d to 446g/d. Okayyyyy. Interestingly, just reducing these carbs to a tenth of this overfeeding level would have given quite easy weight loss for most people, with the fat left alone!

There were snacks too but they don't affect the basic argument.

Jebb is a calories in calories out sort of a person, so fructose is the same as glucose to her. We'll never know how much fructose was fed.

Now let's look at substrate oxidation. With all that increased fat intake what happened to fat oxidation? (All of the values are approx and from the figure)

With a fat intake of 4.5MJ/d fat oxidation was 4.5MJ/d. Neat that!

On 20% overfeeding fat intake went up to 6MJ/d and fat oxidation DROPPED to 3.8MJ/d.

On 40% overfeeding fat intake increased to about 7.7MJ/d and oxidation DROPPED FURTHER to 3.5MJ/d.

On 60% overfeeding fat intake was 8.5MJ/d and fat oxidation seems to have bottomed out at 3.5MJ/d, no further drop.

Three points,

Carbohydrate oxidation went up as carbohydrate intake increased. This cannot happen without insulin. Increased carbohydrate oxidation means increased insulin, certainly at this level of increase of glucose oxidation. Jebb either doesn't know this, and is an idiot, or does know this and didn't measure insulin for a personal agenda. I favour the idiot theory with Jebb. I guess you could argue insulin sensitivity increased but this is a study of gross overfeeding, so that's unlikely.

Fat oxidation decreased with increased calories. What controls lipolysis? Insulin. More insulin, less lipolysis. Less lipolysis means less fat oxidation. Fat is stored more effectively and is locked in to storage. You can't oxidise stored fat.

Body water went up. Water retention means sodium retention (water retention without sodium retention = hyponatraemia = death). Sodium retention is a hallmark of elevated insulin acting on the kidneys.

In a short communication the same group measured leptin and ghrelin levels, which indictaed everything should be hunky dory for return to normal body weight, but clearly things weren't. That's assuming leptin satiates and ghrelin makes you hungry. In a simple balance of energy in vs energy out, weight is controlled by appetite. This being a Jebbish paper, they didn't measure insulin. They didn't measure the primary fat storage hormone. Oh, Susan, how could you not do this?

So what really happened in this study?

Weight gain, to anyone with half a brain, is a phenomenon of the diversion of ingested calories to storage as adipose tissue. Metabolic fuel requirement must be met at the cellular level, above that calories can go to storage as fat. Weight loss means the body gaining access to stored fat calories. Hunger controls eating behaviour when there is no artificial requirement to over eat by 60%. Hunger will adjust food intake until there is an adequate supply of metabolic fuel for the whole body.

If a large chunk of those calories consumed go in to storage, even without overeating, you will maintain hunger until you achieve enough AVAILABLE calories which are needed to run your metabolism. Whether these come from food or bodyfat depend on blood insulin level. High insulin levels lock energy in to fat, so you must eat more food to obtain metabolic fuel. Hence you don't lose weight because energy locked in to bodyfat isn't being used.

You don't need to measure insulin to know it goes through the roof when you eat nearly half a kilo of carbohydrate in a day. You don't need to measure insulin to know it is elevated when you see fatty acid oxidation plummet. You don't need to measure insulin to know it is elevated when you see glucose oxidation rise.

You MUST measure insulin if you want the readers of your scientific publications to think you remotely know anything about weight control and are in a position to advise the nation.

Ultimately, the verdict on Susan A Jebb will be that she she did not measure insulin.


Oh, and weight loss was impossible for some people, they were the ones who got most fatty liver infiltration per unit fructose ingestion. As a guess.

Thanks to Robert for the link to the papers in this post.


Charles R. said...

This is the kind of stuff that just makes me want to bang my head on my desk.

Because they are obviously not stupid people, it is so clearly a religious position that these researchers take time after time. Their approach is just irrational.

Cupcakes said...

Has anyone like Susan Jebb ever seen someone lose weight whilst following her advice?

Morons at the Helm.

jim said...

lose/gain loose/tight

but you already knew that.


Tal said...

Hi Peter

Sorry to post OT. I don't have an academic background in biology or indeed any science (unless you count GSCEs!) but learning anew from your excellent blog is immensely enjoyable - thank you very much indeed. I remember in one post you referred to Mosby's Crash Course in Nutrition and Metabolism - would you perhaps recommend this book for a layman with a real interest and passion (not brought out during my school years!) for the subject? I had a flick through it today in a bookshop and was impressed with the presentation, especially the clarity of the illustrations. I was of course unsurprised to see the lipid hypothesis getting an airing in places - is this just par for the course in all texts of this type? Also, if I buy a copy for study, is there anything else I should be aware of as being 'wrong' from an LC / HF perspective?

Thanks again,


Peter said...

Hi Tal,

I've got the 1998 edition by Sarah Benyon. It's quite clean of the lipid hypothesis, as far as I've noticed, and ought to be cheap as a second hand item... I like it. Easier going than slogging through a full biochemistry text like Leninger.


Lynn M. said...

You wrote "CD32 knockout mice have lower blood glucose than wild type mice." just above the first graphic about CD36 knockout mice.

Did mean CD36 knockout mice?

Kitty said...

Follow the money. Susan Jebb receives funding from the grain lobby. She will never mention insulin for that reason.

webster said...

To me it looks like this was forced overfeeding here, rather than voluntary overfeeding; what the subjects would have eaten under normal circumstances. I'd like to see how the outcome would vary if macronutrient ratios were considered. i.e. overfeeding carbs vs. fats. This abstract shows how de novo lipogenesis occurs under massive carbohydrate overfeeding.

Anonymous said...

Yeesh, another candidate for the bogbrush!

Had you considered whether David Cameron might want an Obesity Tsar? You'd be ideal for the post.

know.nutrition said...

As a 3rd yr nutrition student in cardiff i find this blog...well not as useful as it could have been to be honest. I am carrying out work similar to this and find the topic interesting and feel that somewhere in this article you have some extremely valid points that I will take away and consider.

However, a few references may have helped for your arguments and, as a scientit, i am sure you must appreciate that critical reviews must leave emotions at the door to be valid.

Your argument, which would have been very interesting as a journal letter to the authors, is clouded by your personal feelings towards a particular scientist (which appear ongoing).I have read the paper and while jeb is infact something like the 8th author (unless you have inside knowledge of greater involvement) she or infact the people who wrote the article do not make the sweeping conclusions you suggest. The term Jebish later in your blog is also uncalled for,lol.

I dont know Jeb's work and, as a student only just starting their first research project, I may be an idealist but even if scientists have differing opinions on a topic surely emotion written responses like this can only harm the scientific community and its relationship with the public.

Anyway, as a student i probalbly cant lecture on the ideals of scientific blogging. I will be taking away some of the points you make here to consider in my own work so thank you for them.

Look forward to reading more of your scientific insight in future blogs.

Mark said...

know.nutrition wrote:
"However, a few references may have helped for your arguments and, as a scientit, i am sure you must appreciate that critical reviews must leave emotions at the door to be valid."

Use the index on the right side of the page and the search feature. Likely, a reference you seek has already been given in a prior post.


Peter said...

Kitty, repeat after me, there is no conspiracy. How does this happen? I can't believe it's deliberate, that's why a favour supidity... Perhaps I'm too naive!

T, Yes, deliberate overfeeding, one person dropped out, no explanation given. But ultimately the body still seems to used carbohydrate to organise the storage of fat. Because carbohydrate oxidation appears to exceed consumption (measurements are not 100% accurate of course) I still don't think a lot of de novo lipogenesis would have gone on here. With over feeding carbohydrate without fat, absolutely. Just as soon as your liver is too stuffed with glycogen I'd expect it to start lipogenesis. Foie Gras all over again.

Actually, the absolute lack of de novo fat synthesis does seem a bit odd. I wonder how they managed to ensure that happened????? Does make you wonder what the fructose intake was. Hmmmmm...


Peter said...

Hi know.nutrition,

Good luck with working out what is going on. Hyperlipid is not a textbook, it's what I think. It reflects what I am like and what I find fascinating. Most of Hyperlipid is probably generally correct and there are a fair few astute readers who are likely to tell me when I seriously booboo.

Susan Jebb is a straw man, easy to poke fun at and knock down. She epitomises the direct cause of the current problems people have with making simple diet choices which either improve or damage their health. She sets policy. So, ultimately, when you see a fat person walking down the street, it's Jebb's policy advice that got them there. If you are in the UK.

In general most large group scientific papers have a first author, who does the work (often for a PhD) and a last author who got the funding, planned the project, directed the student and generally decides what goes in to the paper.

The middle authors are frequently "also ran"s. That's just how it is in science (if you can call this science). When you apply for a job they will look at your first author papers. The person interviewing you for your job will be last author on your subsequent publications (if she gives you the job). No brownie points for a middle author paper.


Anonymous said...

At least Susan Jebb isnt (yet) as obese as some of her colleagues

"know nutrition" sounds suspiciously like Chris Cashin, also calling herself Ally and to be found here among many other places

Here you will also meet Catherine Collins RD. Now she IS fat.