Archive for November, 2011

Watching what you eat: foods having delayed effect on appetite

November 28, 2011

On a very low energy diet(often called VLCD), the dieter starts considering each additional item of  food or drink on the basis of the energy it will add.   Science has provided another basis for considering foods:  the subsequent effect on appetite.  I want to list a few where it will be interesting to watch for future research:

1. Milk products:  In those with a low calcium intake, reduce feelings of hunger more than an energy-matched drink. The calcium and protein in milk may be the triggers for this effect.(1, 2)

2. fats and oils

The short-term effect of fats is to reduce the sensation of hunger shortly after the fatty acids from digestion of fats reach the duodenum.   Surprisingly small amounts of oil can have this effect, but in those who eat much fat it is suppressed –  the whole matter of fat digestion is horribly complex (3)   However, improved sensitivity was measured in obese men after 4 days on a VLCD . (4)

Unfortunately, it has been found that eating fats/oils  does not always reduce appetite later, and may increase appetite the next day (5).   This fits with anecdotal evidence – for example, following a cheesecake relapse, a dieter experienced more hunger than usual the next two days, where the same effect was not felt after a protein-binge.

More confusingly, the type of oil is important – for example, fish oil seems to add less energy (that is, result in less fat) than do maize oil or beef fat. (6)

3. Citrates

Lemon juice, and various similar chemicals often added to cordials.   In some people, citrates seem to make it more difficult to adhere to a VLCD.  This may be linked to  the role of citric acid in favouring gluconeogenesis over ketogenesis (7).  (VLCDs emphasise ketogenesis for weight loss.  Making glucose inside the body does burn energy, but seems linked to increased appetite

Research needed:

Most studies emphasise same-day or long-term effects of particular food types.   More reliable studies on two- or three-day effects on appetite and perceived tiredness/energy levels, with titles showing on net searches, would be welcome.

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Footnotes
1. Gilbert JA, Joanisse DR, Chaput JP, Miegueu P, Cianflone K, Alméras N, Tremblay A.   (2011)  “Milk supplementation facilitates appetite control in obese women during weight loss: a randomised, single-blind, placebo-controlled trial.”     Br J Nutr. 105(1):133-43.   http://www.ncbi.nlm.nih.gov/pubmed/21205360

2. Major GC, Alarie FP, Doré J, Tremblay A. (2009) “Calcium plus vitamin D supplementation and fat mass loss in female very low-calcium consumers: potential link with a calcium-specific appetite control.” Br J Nutr. 101(5):659-63. http://www.ncbi.nlm.nih.gov/pubmed/21205360

3. Little, Tanya J. and Feinle-Bisset, C  (2010)  “Oral and Gastrointestinal Sensing of Dietary Fat and Appetite Regulation in Humans: Modification by Diet and Obesity” Front Neurosci. 2010; 4: 178. Published online 2010 October 19. Prepublished online 2010 May 20. doi:  10.3389/fnins.2010.00178   http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2981385/

4.

Brennan, I M,  Seimon, R V, Luscombe-Marsh, N D, Otto, B, Horowitz, M and Feinle-Bisset C (2011). “Effects of acute dietary restriction on gut motor, hormone and energy intake responses to duodenal fat in obese men” International Journal of Obesity 35, 448–456; doi:10.1038/ijo.2010.153; published online 3 August 2010  http://www.nature.com/ijo/journal/v35/n3/abs/ijo2010153a.html

5.http://www.reebokcrossfitone.com/Nutrition/Effect-of-dietary-fat-on-satiation-within-and-between-meals.html?print=1&tmpl=component (does not display well in my browser, but deserves credit for links to the fulltext article

Blundell, JE, Burley, VJ,  Cotton, JR, and Lawton CL  (1993) “Dietary fat and the control of energy intake: evaluating the effects of fat on meal size and postmeal satiety.”  American Journal of Clinical Nutrition, Vol 57, 772S-778S  http://www.ajcn.org/content/57/5/772S.abstract?sid=d31ef1ca-bb08-4d39-9f0b-ec12322c5e74)

6.Jang IS, Hwang DY, Chae KR, Lee JE, Kim YK, Kang TS, Hwang JH, Lim CH, Huh YB, Cho JS. (2003) “Role of dietary fat type in the development of adiposity from dietary obesity-susceptible Sprague-Dawley rats.”  Br J Nutr. 2003 Mar;89(3):429-38. http://www.ncbi.nlm.nih.gov/pubmed/12628037

7. Kreitzman, S.N. (1992)  Factors influencing body composition during very-low-calorie diets   Am J Clin Nutr 56:217S-23S.

Psychology: Why I class it as a science.

November 21, 2011

It is sometimes said that Psychology shouldn’t be classed as a science, because psychologists can’t accurately predict what individual people will do:  in a real science, we expect testable predictions.

To be generous, I will allow all  brain-scan linked psychology to be put under neuroscience, and all chemical-linked psychology to be under psychopharmacology.  I will consider only social psychology and the study of individual behaviours.

It is clear that any situation brings out different responses from different human individuals, and that the range of these responses is predictable.

Some situational responses are very common.  In a previous post  I gave some examples of famous response patterns,  but there is a huge range of psychological research into common effects.  (For a quick start, there are many videos and books from Richard Wiseman .)  However, for every standard response there is a sizeable minority who are non-standard.  Does this invalidate the claim to scientific status for psychology?  Consider the reasons for the range of responses:

To begin with, testing of famous effects has made it clear that different cultures prime us to different response sets.  (Laura Spinney’s article on being WEIRD gives a few examples. )

On the individual level, personality and past experience also prime individuals to particular responses.   Research on resilience gives many examples of this.

Finally, for each of us, there is a probability of a particular behaviour in a given situation – even in rats with strongly conditioned responses there is a degree of variability in response.

So, psychologist have found many aspects of variability in response, and are trying to identify causes and measure their effects – alone and in combination – and are testing their predictions.   That sounds like science to me.  However, they still can’t usually predict what an individual will do. So, is that a fatal flaw?

Let us consider Chemistry – that is a science.  Given a set of chemicals, in a given environment, the outputs are predictable – right?  Well, take burning an archetypical carbohydrate:  CH2O (s) + O2 (g)  – >  CO2 (g) + H2O (g).   Can the chemist predict which of the Oxygen gas’s atoms will end in the carbon dioxide?  Consider the history of producing  isocyanides  :  the proportions of different products from a given starting mix was initially hard to predict, and much research was needed before the exact conditions for high yield were found.   With the invention of microwave ovens, chemists found  a new range of conditions for chemical reactions – and again started by finding out the changes in  mixture of products from changes in process.  ( One example is the processing of methane, of interest to the natural gas / syngas industry.)

So, I argue that Psychology can be classed as a science precisely because  (like research Chemists) the researchers accept that there are limits to their knowledge,  that they must measure reality to form ideas of what might be happening (hypotheses),  and that their predictions (from hypotheses) of the results of given processes must be tested against reality before a strong theory can be developed.

Do the politicians think we have no memory?

November 14, 2011

“The ignorance of one voter in a democracy impairs the security of all.” — John F. Kennedy, 1963

Here  in Oz, it is starting to feel as though the Federal opposition think the voters are really, really ignorant of law and history, and that they want to keep things that way.  They seem to be going on the premise that

You can fool all of the people some of the time, and some of the people all of the time, but you can’t fool all of the people all of the time.  The trick is to fool enough to get elected into power.

Unfortunately, the media seem to be going along with it, to the detriment of our version of democracy.

I started to wonder how dim the average journalist is when no-one challenged the claim that, if a proposed tax did not get passed by parliament, the current government should (with voice tones suggesting “are required by tradition to…) dissolve parliament and hold an early election.  Now, I remember several occasions when financial bills were not passed, were resubmitted and rejected again, and the government of the day had a “double dissolution trigger” which they might choose to use.  Usually they did not.  Therefore, the clain was false – however, the press let it through unchallenged.

Then the Opposition started saying that Australia can’t be run by a Coalition – referring to the agreement between the Labour Party and the Greens.   They suggest that it is in some way wrong for Labour to trade favours with the Greens.

Not even the satirists have commented that we were run by the Liberal/National (a.k.a Country Party) coalition for many years (they joined in 1922), and that “The Opposition” is that same bunch, so famous that Wikipedia    gives them as the primary meaning for ” Coalition” in Australian politics.   None of the political journalists have mentioned the thousands of times Liberal policies were shifted to meet the demands of the gerrymandered rural electorates.

Now the Opposition is suggesting that the Labour party is wrong or weak to trade favours with the Independent Senators, who hold the balance of power.   Strangely, no-one has mentioned former Senator Brian Harradine, who served from 1975 to 2005, and strongly represented the conservative Christian viewpoint for many years by enthusiastically exploiting his position as a “balance of power” senator.    I have heard no-one  in the current commentariate  ask whether the series of (now) respected former PMs who did dubious deals with hin were, by that argument, wrong, or weak.  (At the time, it was a common left-wing  grumble about lack of courage – but dismissed by The Coalition, who liked many of his opinions.)

I wouldn’t be so annoyed by the Opposition’s attempts to sway voters if (i) they weren’t misleading voters as to the traditions and Law of our parliamentary system; (ii) if they hadn’t done exactly the same themselves; and (iii) if the current affairs programmes and satirists were hammering them for their hypocrisy.

The trouble is that younger voters haven’t lived through the events which this campaign ignores, schools haven’t the time to go through the details of past political horsetrading, most children learn just enough about the system for just long enough to pass their school tests, and most people don’t read political history for fun.  If the journalists don’t challenge them publicly, politicians can spread false views of Law and history.   Then we get the downside of democracy: the lazy and below-average together vastly outnumber and outvote those who are both gifted and thoughtful.

Where the lazy, average, and  below-average are not properly advised by the knowledgeable (or, even worse, are led by demagogues to distrust and mock those of high intelligence),  they have fewer thoughtful members to debate with the gifted and thoughtful and thus are less able to make a strong democracy.  Instead  we see the situation Mills warned of:

“A people may prefer a free government, but if, from indolence, or carelessness, or cowardice, or want of public spirit, they are unequal to the exertions necessary for preserving it; if they will not fight for it when it is directly attacked; if they can be deluded by the artifices used to cheat them out of it; if by momentary discouragement, or temporary panic, or a fit of enthusiasm for an individual, they can be induced to lay their liberties at the feet even of a great man, or trust him with powers which enable him to subvert their institutions; in all these cases they are more or less unfit for liberty: and though it may be for their good to have had it even for a short time, they are unlikely long to enjoy it.” — John Stuart Mill, Representative Government, 1861  (My emphases)    

 

“It’s Just Water” … well, no. Early weight loss in dieting.

November 7, 2011

One of the common statements in low-energy dieting is that “The first couple of kilos is just water.”   (That is, once you allow for the change in bowel contents.) If it is just water, how can one lose two litres of water and not feel the effects of dehydration?

To understand this, we have to understand a little human  biochemistry.

Glucose,  glycogen stores, and water

Our brains and muscles “burn” glucose – a simple sugar, found in many carbohydrate rich foods (for example, cane sugar is one fructose molecule bound to one glucose molecule).   It  is disassembled to release chemical energy, carried in the form of a small molecule called ATP (Adenosine triphosphate).   Glucose is so important that our bodies can use other molecules and energy from other foods to make glucose (gluconeogenesis).

As with other important materials, our bodies store glucose for later use.  The stores are not glucose itself – they are molecules which the body can take apart for glucose.  The first storage is as a molecule called glycogen, stored in the liver and muscles;  secondary storage is as fat.  When there is plenty of glucose and ATP,  insulin promotes the conversion of glucose into glycogen.

When there is little ATP and little glucose, our cells’ first response is to disassemble glycogen to keep the blood sugar level up.   So, in dieting, our cells first use the glycogen stores. A common estimate of adult glycogen stores is 400 to 500 g.   However, glycogen is not stored alone – like glucose, its pure form is not a soft or liquid substance.  It is stored with three to four times its weight in water (1).   So, in the initial stages of dieting, the glycogen stores are used up and the associated water is released.

It takes energy to make and store glycogen, and to transport its related water.  So, in using up glycogen, dieters  reduce the stored energy within their bodies.   Therefore, the weight loss is not just water, and does reflect a real improvement in body mass – just not as much in terms of fat-equivalents.

After the diet

When the dieter returns to a weight-maintenance eating pattern, it is reasonable for ver to rebuild ves glycogen stores.  So, ve must plan for that: ve must be aware that the first couple of kilos (after accounting for bowel contents) will not be fat, will be valuable for maintaining blood sugar levels, and are to be expected to be back very soon after leaving off the strict regimen (in days, not weeks.)  An immediate effect is that the target weight should reflect this expectation: if ve wishes to weigh 65 kilos, ver goal in dieting would be 63 kilos (minus an amount  for bowel contents depending on diet) .

Upsides and downsides of continuing low-energy dieting for more than the water-loss period

Upside

The body does not burn its fat stores significantly until the glycogen is low.   This is one reason to value the rapid initial glycogen and water weight loss stage, and to continue beyond it.

A second reason is not commonly known:  the brain relies on glucose for energy until blood sugar levels have been low for some time, but after about three days it starts using smaller molecules called ketone bodies (the things which give dieters ketosis, resulting in  “nail polish breath (2) “).  From about 40% after three days of starvation (3), after about a month it can get up to 7o% of its energy from ketone bodies.  In human evolution periods of  low-carbohydrate diets  – and real hunger – were common, so is reasonable that our bodies are adapted to use other energy sources.  It is now suggested that there may be benefits to deliberately triggering this shift in brain metabolism. (4)  As with decreased exposure to diseases with modern lifestyles (5,6), decreased exposure to hunger may not be entirely to our benefit.

Downside

There is one main downside:   Low blood sugar is linked to various problems, including difficulty  controlling impulses.  In dieting these are not as severe as those diabetics may experience , but a degree of crankiness is to be expected – especially in the days before the brain shifts to using ketone bodies.

A second downside is the risk that low energy intake may be associated with a poorly balanced diet with poor essential nutrient levels.  One may get away with this in the short term, but over longer periods one must plan very carefully.   I feel that this is minor, as there are several well balanced VLCD (very low calorie diet) systems available.  However, unless the dieter is competent in dietary analysis, it would be best to have nutritional advice from a University-trained source.

A third downside is that the process is a physical strain – which is why the packaged approaches recommend medical supervision: there is a risk that unrecognised problems (such as liver failure) may flare up under the stress.

Conclusion

It isn’t just water, and it is a sign that you are, at least, not getting fatter.  The hard work is worth it – but watch your temper and watch your nutrition.

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1.  Kreitzman, S N  (1992)  Factors influencing body composition  during very-low-calorie diets Am J Clin Nutr 56:217S-23S.   http://www.ajcn.org/content/56/1/217S.long

2. Note that this mild ketosis is different from the severe and life-threatening ketoacidosis (commonly from diabetes or alcoholism), where the smell is stronger and medical attention is required.

3.Hasselbalch, SG; Knudsen, GM; Jakobsen, J; Hageman, LP; Holm, S; Paulson, OB (1994). “Brain metabolism during short-term starvation in humans.”. Journal of cerebral blood flow and metabolism 14 (1): 125–31. doi:10.1038/jcbfm.1994.17. PMID 8263048.

4. http://www.ncbi.nlm.nih.gov/pubmed/20188215   , http://www.ncbi.nlm.nih.gov/pubmed/20009300

5. Committee on The International Study of Asthma, Allergies in Childhood (ISAAC), Steering Committee. Worldwide variation in prevalence of symptoms of asthma, allergic rhinoconjunctivitis, and atopic eczema. ISAAC Lancet. 1998. pp. 1225–32.

6. Nowak D, Wichmann H-E, Magnusson H. Asthma and atopy in Western and Eastern communities- current status and open questions. Clin Exp Allergy. 1998;28:1043–6. [PubMed]