Paleolithic Diet Clinical Trials, Part V

Dr. Staffan Lindeberg's group has published a new paleolithic diet paper in the journal Nutrition and Metabolism, titled "A Paleolithic Diet is More Satiating per Calorie than a Mediterranean-like Diet in Individuals with Ischemic Heart Disease" (1).

The data in this paper are from the same intervention as his group's 2007 paper in Diabetologia (2). To review the results of this paper, 12 weeks of a Paleolithic-style diet caused impressive fat loss and improvement in glucose tolerance, compared to 12 weeks of a Mediterranean-style diet, in volunteers with pre-diabetes or diabetes and ischemic heart disease. Participants who started off with diabetes ended up without it. A Paleolithic diet excludes grains, dairy, legumes and any other category of food that was not a major human food source prior to agriculture. I commented on this study a while back (3, 4).

One of the most intriguing findings in his 2007 study was the low calorie intake of the Paleolithic group. Despite receiving no instruction to reduce calorie intake, the Paleolithic group only ate 1,388 calories per day, compared to 1,823 calories per day for the Mediterranean group*. That's a remarkably low ad libitum calorie intake in the former (and a fairly low intake in the latter as well).

With such a low calorie intake over 12 weeks, you might think the Paleolithic group was starving. Fortunately, the authors had the foresight to measure satiety, or fullness, in both groups during the intervention. They found that satiety was almost identical in the two groups, despite the 24% lower calorie intake of the Paleolithic group. In other words, the Paleolithic group was just as full as the Mediterranean group, despite a considerably lower intake of calories. This implies to me that the body fat "set point" decreased, allowing a reduced calorie intake while body fat stores were burned to make up the calorie deficit. I suspect it also decreased somewhat in the Mediterranean group, although we can't know for sure because we don't have baseline satiety data for comparison.

There are a few possible explanations for this result. The first is that the Paleolithic group was eating more protein, a highly satiating macronutrient. However, given the fact that absolute protein intake was scarcely different between groups, I think this is unlikely to explain the reduced calorie intake.

A second possibility is that certain potentially damaging Neolithic foods (e.g., wheat and refined sugar) interfere with leptin signaling**, and removing them lowers fat mass by allowing leptin to function correctly. Dr. Lindeberg and colleagues authored a hypothesis paper on this topic in 2005 (5).

A third possibility is that a major dietary change of any kind lowers the body fat setpoint and reduces calorie intake for a certain period of time. In support of this hypothesis, both low-carbohydrate and low-fat diet trials show that overweight people spontaneously eat fewer calories when instructed to modify their diets in either direction (6, 7). More extreme changes may cause a larger decrease in calorie intake and fat mass, as evidenced by the results of low-fat vegan diet trials (8, 9). Chris Voigt's potato diet also falls into this category (10, 11). I think there may be something about changing food-related sensory cues that alters the defended level of fat mass. A similar idea is the basis of Seth Roberts' book The Shangri-La Diet.

If I had to guess, I would think the second and third possibilities contributed to the finding that Paleolithic dieters lost more fat without feeling hungry over the 12 week diet period.


*Intakes were determined using 4-day weighed food records.

**Leptin is a hormone produced by body fat that reduces food intake and increases energy expenditure by acting in the brain. The more fat a person carries, the more leptin they produce, and hypothetically this should keep body fat in a narrow window by this form of "negative feedback". Clearly, that's not the whole story, otherwise obesity wouldn't exist. A leading hypothesis is that resistance to the hormone leptin causes this feedback loop to defend a higher level of fat mass.

please forgive me....

for my absence....
i have lots of packing to do and little access to a computer for next two weeks.
but i promise, mid january, i'm back to my old self again. 
xoxo, pink wallpaper

Being Brilliant vs. Writing Well

In the vast world of academic Computer Science publishing, I am about to tell you the greatest secret of all:

You can make up for lack of genius by being a good writer.

Being a good writer will never guarantee a paper acceptance. But I'll tell you, if your paper is like butter for a reviewer to read, it makes it all the more difficult for them to tear it apart. If your writing is crisp and clear and sharp and snappy, it makes reviewers feel joy in the hearts. Especially compared to the other poor abuses of the English language they had to sludge though before your paper walked through the door.

It's actually quite easy to learn to write well. Here are some tips:

1) Practice, practice, practice. A blog can really help, actually. Twitter probably not so much. You want to aim for cogent prose.

2) Read a lot. Read well-edited publications - newspapers, magazines, journals. Journalists are excellent at grabbing your attention and keeping it. This skill is invaluable in scientific writing.

3) Less is more. You are not getting paid by the word here. (In fact just the opposite - many conferences have page charges if you go over the limit!). It is not necessary to give every gory detail. It is highly unlikely you need to paste code into your paper. Just convey the information that is most important - what is it you want people to take away after reading your paper?

4) Once you're confident, take some risks. I know your 3rd grade teacher told you all of these things about structure and topic sentences and a conclusion section and an outline section and all that jazz. But really you need to figure out your own style that best helps you convey clear ideas.

5) Proofread your paper very carefully before submitting it. I am shocked when I read papers with grammar errors, spelling errors, and typos, particularly from senior academics who are fluent English speakers. Take the time to proofread, or outsource. (Occasional errors are understandable, but a paper should not be littered with them).

6) Practice!

Publication Venues in Computer Science

In academic Computer Science, there are basically three publication venues that "count": peer-reviewed conferences, peer-reviewed journals, and peer-reviewed workshops/symposia. There are of course many other perfectly credible ways to publish one's work (e.g., technical reports, books), but these are the top three.

Unlike in most scientific fields, including our closest cousins Engineering and Mathematics, journals are not the de facto place to publish papers. I can't speak for all subfields of CS, but basically everyone I know only publishes in journals because they feel they have to (e.g., multi-disciplinary tenure and promotion committees that expect journal publications, research rankings organizations that still don't seem to 'get' conferences, etc.). Some subfields this is not the case, such as in interdisciplinary fields like Bioinformatics and CS Education, but for most major areas of CS, conferences are where the action is.

For these fields, the top conferences have extremely low acceptance rates, many less than 17%. The program committees are comprised of the top scholars in the field. And in some fields, anyone who is anyone attends these conferences, so managing to get a paper accepted is a pretty big deal that gets a researcher much visibility.

Some journals have similarly rigorous standards of review and are known for their quality, for example the IEEE Transactions and ACM Transactions family of journals are highly regarded. There are occasionally other journals that are good, but the vast majority are either decidedly mediocre or utter rubbish. We don't really have any comparable C/N/S type journals.

Workshops and symposia generally have a much higher acceptance rate than conferences and journals, but they are still peer-reviewed and are often archival (e.g., ACM Digital Library, IEEE Xplore). They have quite a few advantages. First, they are usually co-located with a conference, which means you can often go to both on your University's dime. Second, they present a fantastic opportunity to float half-baked ideas and get one-on-one feedback from your peers. And third, oftentimes workshops are the only place you can meet other scientists interested in the same area of specialized research as you, which nearly always leads to good things.

But the most useful thing about conferences and workshops over journals is that you have the opportunity to tell potentially hundreds of people about your work. These are all people who learn your name and face and start to match it to a research area. This is invaluable, because it leads to professional relationships that will see you through your career - jobs, funding, tenure/promotion letters, etc.

Journals don't really get your name and face out there as well, unless some news outlet picks up on your article. People do read journals, but I suspect most readers associate papers more strongly with an institution than a name, particularly if it's a new name on the research scene.

So I think it's nice to have a diverse portfolio when it comes to publishing. It's good to have a mixture of papers in the top conferences with low acceptance rates, in journals that are well-respected, and in workshops that are useful to the researcher.

2010 was a very interesting year...
we uprooted our life in charleston and moved to beaufort, we found out we were having a baby boy, i ate my first fried pickle (and loved every minute of it), i spent 13 wks on bed rest, my daughter turned 3, a best friend survived a near fatal car accident, i had the honor of being published, i turned 31, we made new friends, i gave birth to a healthy baby boy, i joined jazzercise (and i might have dropped out), my husband and i started running again (and then maybe stopped), i expanded my company, we cooked a lot, i grocery shopped at walmart, i accomplished potty training (but not w/out a good, hard fight and maybe some tears), we drove 3,000 miles in a wk w/out the kiddos....but the best part was the time spent w/ my hubbie and two kids that i will never be able to replace.
so what does 2011 have going on???  well, my hubbie has a new job and we are moving to columbia, sc and that's about all i know for sure....but i am excited to see how it all unfolds!!

**to beaufort, our friends, and my parents- thank you from the bottom of my heart for a beautiful town and a very memorable year ;)