Posts by Chemist

Re: What is human fat anyway?

"I don't think it's nice unsaturated stuff like goose fat, I reckon it's nasty saturated stuff like pork or beef fat...."

You don't need to think here's a measurement - it's quite a mix with lots of variation, but there's quite high levels for both saturated and unsaturated fat.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1205373/pdf/biochemj01003-0098.pdf

Re: It's a lot easier to just not eat it to begin with.

"Unless you are a serious athlete, you aren't going to exercise enough to lose weight. "

That's not true. It's very hard because it needs commitment.

Consider this : most people gain weight slowly - say 5kg a year, that's ~40000 Cals, and that's just ~110 Cals/day Even a weight gain of ( a huge) 15 kg a year is still equivalent to just 350 calories a day and that's just 1 chocolate bar. Weight gain is pernicious, not sudden. When people do try to seriously do something about it they want instant results hence the fad diets etc. If they try by dieting, unless by serious starvation, to lose weight the weight loss will so slow as to be disheartening given the hunger hence the constant failures.

If you merely diet you have to reduce your intake to 'normal, and that takes time to establish as everyone is different, different outputs, basal rates, environments, biological variation and basic diets. Compounding this is the measurement problem. (Day-day variation in weight can be quite large, even ± 1kg is a range of 16000 Cals, almost entirely water retention/loss but tracking true weight change is made very difficult when you might only be losing 0.05kg/day.)

Once normal ( for you ) calorie intake is known you then have to decide how much to lose and also compensate as you say for the dropping of metabolic rate that accompanies semi-starvation. What that is for any individual ?. If it's say 200 Cals/day (which is a <10% drop in metabolic rate) then that has to be added to the amount you have to diet. If you want to lose 0.7 kg/week (say) that means reducing intake by 1000 Cals/day and that's when it becomes hard. Most people will feel very hungry, cold and depressed. Normal social life becomes hard and any backsliding a cause for guilt. Is it any wonder that most overweight people fail ?.

But remember that weight went on slowly, without most people noticing, it's best removed that way. It does require long-term thinking. But if you've managed to establish a weight neutral diet then even walking 2 miles extra a day will lose you ~9 kg in a year. There are caveats to this, as you lose weight your exercise is less costly in Calorie terms so the loss/mile will gradually slow, you need to be careful about your 'normal' consumption drifting as one choc. bar will negate 2 whole days exercise. The gain is you probably won't feel as hungry as if you'd seriously reduced your calorie intake, you'll get fitter, you'll feel better about yourself, you'll go quite some way to reducing your risk of type 2 diabetes, and if you do this exercise outdoors you'll probably boost your Vit D levels.

Me, I did a lot more than 2 miles a day, I was lucky my job allowed me enough time to do this , running before breakfast, walking instead of lunch, and stomping around the hill in the evenings I did backslide and doing as much exercise in winter where I live was very difficult. But I lost 35kg and never regained it. I still average ~500 Cals/day exercise but my Calories intake has risen to match it.

Footnote : I gained ~25 kg over ~ 5 years when my only exercise was working all hours refurbishing a house that we bought. Lots of isometric exercise but not as much aerobic. Lots of eating of convenience food/beer. I f you remember that equates to just ~100 excess CAls/day

"Argument from fallacy; if your intake was reasonable, you would not need to lose weight."

Of course not. The point is to return to a normal calorie consumption ( for you) that keeps your weight neutral - this isn't dieting it's just returning to normal. At this point you can diet, exercise or both .All will work, the exercise will be hard but you'll be fit and not suffer hunger, & retain/increase muscle.

If you chose diet then you'll be hungry and lose muscle and have lower basal metabolic rate

"Extra exercise accounts for such a small amount of your calorific expenditure" - depends how much you do - when I was losing 35kg I would usually do 800-1800 Cals a day. You can lose 1kg a week or more doing that. It's a lot day-in day-out but it worked (for me)

"Exercise is fine for health, but it will do nothing for weight unless you also constrain intake."

If your intake is reasonable then exercise will reduce your weight, if your intake is enormous so will you be unless your an athlete in training.

"To burn off a pack of chocolate digestives you'd be jogging for 4 hours."

Scarcely a reasonable diet !

"Err.....no. Fats are triglyceride esters of long chain fatty acids. Short chain fatty acids really don't count. You're not going to build up body fat through absorption of acetic / propionic/ valeric / lactic acids (or their salts or esters) - which are what are produced in the rumen."

Err.... yes

"http://www.vivo.colostate.edu/hbooks/pathphys/digestion/herbivores/rum_absorb.html"

The three major VFA absorbed from the rumen have somewhat distinctive metabolic fates:"

Acetic acid is utilized minimally in the liver, and is oxidized throughout most of the body to generate ATP. Another important use of acetate is as the major source of acetyl CoA for synthesis of lipids.

Proprionic acid is almost completely removed from portal blood by the liver. Within the liver, proprionate serves as a major substrate for gluconeogenesis, which is absolutely critical to the ruminant because almost no glucose reaches the small intestine for absorption.

Butyric acid, most of which comes out of the rumen as the ketone beta-hydroxybutyric acid, is oxidized in many tissues for energy production.

"Fats are triglyceride esters of long chain fatty acids"

Well oddly enough having been a chemist for 44 years I know that.

"http://en.wikipedia.org/wiki/Fatty_acid_synthesis"

Fatty acid synthesis is the creation of fatty acids from acetyl-CoA and malonyl-CoA precursors through action of enzymes......

Re: A bomb calorimiter does not mimic digestion or metabolism

"Cholesterol in the diet is damned hard to adsorb" Not too hard it seems

"Absorption values ranged widely from 29.0% to 80.1%"

http://www.ncbi.nlm.nih.gov/pubmed/9925660

Re: A bomb calorimiter does not mimic digestion or metabolism

"We do NOT store excess sugars as fat,"

That is simply not true. Glucose is stored as glycogen AND also converted to fat. This is most evident when excess is consumed. The body has a limited capacity for glycogen but as is all too evident an almost unlimited capacity for fat, whether eaten as such or produced from glucose.

There are countless refs. to this : here's one :

"Hepatic and whole-body fat synthesis in humans during carbohydrate overfeeding"

http://www.ncbi.nlm.nih.gov/pubmed/9174472

"Simple - if eating fat was what made you fat, then sheep and cattle wouldn't be fat.......but they are."

I was confused and now you've explained it I'm afraid it's not a true test of the hypothesis

The test really is to to find a animal where eating a high fat diet ( to excess - it always has to be more calories than needed) DOESN'T result in weight gain. I don't know of one - anyone else ?

By the way sheep/cattle diets do contain high levels of fats, or rather short chain fatty acids - the bacterial action in the rumen etc. produces them. In fact ruminants get a relatively small amount of carbohydrate after the bacterial digestion. Glucose needed for brain activity at least is produced from the fatty acids.

"Cattle and sheep are our primary sources of animal fats. Both - if allowed - will gorge themselves and get fat."

Not sure what point you're trying to make. Carbohydrates are readily converted into fat in mammals and in ruminants complex carbohydrates can be converted to a variety of products by resident bacteria. Most foods can substitute for others at least in the short term, for example protein can be burnt for energy and also converted into glucose. Fats can be burnt for energy or converted to glucose via 'ketone bodies' although there are several problems with long-term use of diets based solely around this approach including osteoporosis, kidney stones, and possible Vit C deficiency.

Example : drink a pint of sugar solution. It'll be adsorbed very rapidly, and your blood glucose level will soar - unless you are a well-trained and exercised athlete the storage of the glucose will rapidly overwhelm your ability to store it as glycogen and as rapidly as possible much of it will be converted to fat If you eat complex carbohydrates that are absorbed more slowly the glycogen storage gets a chance to compete. But in the end it's much the same eat more carbohydrates or fat than you need and it will all end up as fat ( once your glycogen stores are full)

Re: Great article, questionable title though...

"Genes (or, better, clumps of molecules we call "genes") are inherent part of the living beings, these molecules do not "code" anything, not any more than, say, crankshaft "codes" anything in the internal combustion engine."

Bit pedantic. Genes code for proteins. You can't use a gene instead of a protein. You can make as many copies of the protein from the gene as time allows. Each 3 nucleotides on the gene (codons) determine the next amino acid to be added to the protein being synthesised. I don't know how you would describe a translation like this from codons to amino acids without calling it a code of some sort. There are even codons to terminate and initiate synthesis. The translation can be tabulated It's more like the punched card in a Jacquard loom. It defines and controls the process but it makes cloth. In a completely different process it also provides a template for copying itself.

Re: Most treatments have no need for either genomic or proteomic diagnostics

" we are using supercomputers to make the decision a "yes/no" not a "choose from these 106 ". Every human in unique, why shouldn't the treatment be?"

I agree and it can be a very simple decision. For example a certain cancer may have 10% of a patient population with one gene variant and the remainder with another. If you can judge with an easy test, which is which, then you can potentially choose the most appropriate drug. I know an example where this is so.

Re: Most treatments have no need for either genomic or proteomic diagnostics

"Or even alcoholism."

The propensity to alcoholism (or other addictions) or it's effects on the individual are very likely to be genetically determined.

Re: New study shows dietary fat doesn't cause problems

"I thought diabetes was always associated with carbs, not fat."

Type 2 diabetes is still rather a mystery. But certainly being overweight or obese, and lack of serious regular exercise are correlated with increased rates. It's got a generic component. (Of course you will always find someone who is obese, does no exercise, smokes 80 a day and lives to 90 but that is the tail of a distribution.)

What I've gathered (it's not really my area of expertise) : High blood glucose drives the production of insulin as a signaling hormone in an attempt to reduce the damaging effect of high levels. If, the mechanisms driven by insulin for some reasons fail to bring it down then a vicious circle of greater and great demands for insulin ensues. This can eventually destroy the insulin producing cells.

The mechanisms that reduce insulin include muscle/liver absorbing glucose and converting it to it's storage form glycogen. This is where the exercise comes in Exercise at first uses stored glucose leaving the exercised muscles/liver able to absorb more. If you don't exercise and esp. if your muscle mass is low the very mechanism that normally reduces blood glucose is blocked. If you have a lot of stored fat it can fueling metabolism again allowing blood glucose to increase over normal. This all is really a rate effect. Slow glucose release from the gut allows other (slower) mechanisms to absorb the glucose, for example, converting glucose to fat.

There are many mechanisms/enzymes/signaling pathways involved in this so it's no suprise that individuals and their genetics vary greatly. There are a number of refinements to all this, for example, exercise greatly increases the ability and extent of muscle to absorb glucose rapidly and also mobilise fat . Complex subject.

Re: Put down the pie

"Are you saying you didn't change your diet at all? You ate the same but increased the amount of exercise you did? Of course, this is possible, but it's a stupid way to lose weight."

I've documented what i did here before but briefly :

I calorie counted as well as I could. I started on ~2000 Cals/day doing my normal level of exercise. Careful checking of my weight revealed that I was slowly gaining weight so I reduced to 1800 Cals/day and after a few weeks I was stable. The exercise was then ramped up - of course diet changes day-to-day, I estimated as well as I could and over the years refined the estimates of exercise. In winter it was hard as I live in a hilly rural area and it's pitch black, so mostly it was case of keeping reasonably stable. In summer I'd often do 1800 Cals/day running, hill walking & cycling.

It's not a stupid way to lose weight as dieting reduces metabolic rate, leaves you feeling hungry all the time AND, far more importantly makes you lose muscle as well as fat. It's controlled starvation. Keeping to a modest exercise rate ensures that muscle is retained and fat is burned ( along with carbohydrates of course) I even managed a few beers and a curry each week.

Re: Put down the pie

"The amount of exercise needed to burn off calories simply makes exercise an unrealistic method of weight loss."

Well you can do it - I lost 35kg over ~3 years by just that. But you are quite correct it is a massive commitment and unrealistic unless your work/life allows for it or you're actually an athlete in training.

That loss BTW averages to just 250 Cals/day

(OTOH it's estimated that hunter/gatherers from 10000 years ago spent ~~1300 Cals/day in exercise - which very roughly equates to 0.15kg of fat)

Re: Food, glorious fo--, wait, what ARE all these ingredients?

"I wonder if fast bread like this gives the yeast time to break down the gluten."

Yeast doesn't 'break down' gluten. If you have a good ref. which says otherwise then post it

Re: New study shows dietary fat doesn't cause problems

"People see that fatties are eating a lot of fat (but also lots of carbs) and *assume* it's the fat that makes them fat. It's not. It's the carbs. Eating fat does not make you fat anymore than eating carrots makes you into a carrot."

Fat is a good fuel, that's why we store it - for the bad times esp. It's a great fuel IF you actually use the calories it contains. I can't imaging what you think happens to this "more efficiently" processed fat IF you don't actually use the calories it contains - do you think that this "efficient processing" makes it disappear into thin air ? Or do you really believe the bacteria in your gut can metabolise excess fat in the diet without consequence. At the very least you'll get VERY hot. Food is measured in calories for a very good reason. 100g of fat is 800,000 calories or 3MJ. If that's metabolised, by you or bacteria, unless you lose a lot of it as high energy waste (like methane) the metabolism will result in a good proportion of 3MJ appearing as heat. If a large proportion IS converted to methane that's in the order of ~~50L (which is flatulence with a vengeance)

BTW do you really imagine that all the food you eat is processed by bacteria first ?

"I would think if you built the electrolysis plants near the output of various sewage treatment plants (NYC, etc) that discharge back into the ocean, you could readily be bringing that water's salinity,"

Except ( and forgetting the previously mentioned severe environmental effects ) you'd merely be putting back the sodium & chlorine that you took out in the first place !

Re: re:Electrolysis of brine produces as much chlorine as hydrogen

Potentially hypochlorite can be decomposed to NaCl and oxygen but the overall problem is the proportion of the energy budget being used to produce a high energy unwanted material.

Re: re:Electrolysis of brine produces as much chlorine as hydrogen

"Ultimately you get HCl and O2,"

You don't . Potentially if you allow the chlorine to react with the sodium hydroxide you get a mix of NaCl and NaOCl. NaOCl is hypochlorite bleach and environmentally very damaging

Re: re:Electrolysis of brine produces as much chlorine as hydrogen

"So if you try to electrolyse sea water this just happens, you can't prevent it as a by-product?"

There's some work on-going into selective electrodes but usually what happens with electrolysis is that at low current density selectivity might be achieved (depending on the characteristics of the competing ions) but at the sorts of current density required for production the selectivity is lost again.

In cases where fresh water supply isn't a problem then that is likely to be a preferred option. Even then I suspect that fairly pure water will be needed. I haven't worked it out but the energy cost of distilling water to purity it is much lower than the energy cost of electrolysis which (at 100% efficiency !!) is ~280kJ/mole - so 280kJ for 2 grams of hydrogen. With the real efficiency factored in the energy costs are ~~20 MJ/m3 of hydrogen gas + water costs + compression costs.

Usually in electrolysis of brine to manufacture chlorine they use pretty pure solutions which are much more concentrated than sea-water. The membranes used to separate the anode/cathode compartments are very expensive and prone to blockage/poisoning as are some electrode materials.

A possible non-electrolysis route is thermal decomposition of steam at high temperatures in the presence of a material that will capture the oxygen. The capture material must itself be capable being regenerated in a separate step. This is still at very early stages AFAIK

Re: re:Electrolysis of brine produces as much chlorine as hydrogen

Why bother with seawater anyway - pure water + several other electrolytes just gives hydrogen and oxygen directly

Re: re:Electrolysis of brine produces as much chlorine as hydrogen

Oh no, I'm afraid not. The electrolysis reaction is :

2NaCl +2H2O -> H2 + Cl2 + 2NaOH.

So to get 1 mole of hydrogen you also get 1 mole of chlorine - it doesn't matter what the concentration is. The volume of hydrogen produced is exactly the same as chlorine.

You can't just dissolve the chlorine back - it's a nasty, nasty reactive & toxic gas - it's not the same as chloride ion.

"As for releasing nasty gasses you could just dissolve them straight back in, without noticeably affecting the concentrations."

No, sorry. Electrolysis of brine produces as much chlorine as hydrogen (~35 times as much by weight of course)- it's the basis of chlorine, sodium hydroxide ( and hence hypochlorite bleach) production. Generating significant amounts more of hydrogen from brine would overwhelm the environment with chlorine and probably sodium hydroxide.

Re: Dreaming @Tom 7

""Hydrogen conversion (electricity->hydrogen->electricity) was over 85% efficient in the early 90's - so better than nuclear at 40%.""

Absolute garbage- and I've got some electrochemistry patents to my name. Even electricity> hydrogen is ~~60% efficiency.

"It deals with rising sea levels too. What's not to like?"

I assume that's a joke

Re: Because then we're probably not alone

"If life spreads around the universe it only has to happen once in the lifetime of the universe."

Basically bollocks - maybe true but so, so unlikely - it's a big,hard, difficult universe out there.

Re: Because then we're probably not alone

"t only has to happen once in the lifetime of the universe."

It's a huge, huge distance to anywhere. Doesn't make it impossible. But at the mo' it's just organic compounds, not DNA, RNA whoa. Wait for the data.

"Thus the commentards have spoken."

You are quite wrong (as usual) my anonymous 'friend'. But reading comments here and on other occasions, something is wrong somewhere. Some people have problems with memory leaks or crashes, others don't. Is there a common thread ?.

I use the same version of FF on 1GB, 2GB, & 8GB memory machines ranging from a single core atom & celeron 32 bit to the 64bit machines dual-core AMD & intel upto latest 4 core i7 and have a very similar experience on all (although naturally some are LOT faster than others) . Few crashes and memory usage around 600MB with ~10 tabs open, no obvious leaks. That experience (since ~2006) is limited to just Linux. It would be interesting to see if there is any correlation with OS or maybe it's some hardware thing.

BTW we all know 1080p in 1 bit of RAM is silly.

"So you repeated browser crashes (once a day for FF is not uncommon) probably go unnoticed."

Would you like an upvote out of pity ?

"Well if you are running Linux, you are used to patching and compiling your own kernels, as well as spending hours on a command line fixing dodgy software."

BTW I know, anyone who has read reviews on Linux distros (here and elsewhere) knows and I suspect YOU know that you don't need to compile a kernel (or use the command-line to install Linux)

And as for your comment about spending hours fixing dodgy software - beneath contempt !

Re: Forgetting something Mr Chemist?

"What would one use to download Konqueror or an ftp client or even wget?"

They all come with my preferred OS.

Re: Ten years and still waiting...

" Ten years and still waiting...

...for a Firefox version that won't crucify a PC with more than a few tabs open."

You should use Linux !