When we lose weight, where does the fat go?

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When we lose weight, where does the fat go?

This topic contains 18 replies, has 14 voices, and was last updated by  bigbooty 6 years, 7 months ago.

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  • Hello,

    My name is James Dalley and this is my first post on this forum.

    I was wondering whether anyone had any comments or insights into the study of where our fat goes when we lose weight, the focus of a paper published in the British Medical Journal today.

    See below for a media release about the paper:

    When we lose weight, where does the fat go?

    Despite a worldwide obsession with diets and fitness regimes, many health professionals cannot correctly answer the question of where body fat goes when people lose weight, a UNSW study shows. The most common misconception among doctors, dieticians and personal trainers is that the missing mass has been converted into energy or heat. “There is surprising ignorance and confusion about the metabolic process of weight loss,” says Professor Andrew Brown, head of the UNSW School of Biotechnology and Biomolecular Sciences. “The correct answer is that most of the mass is breathed out as carbon dioxide. It goes into thin air,” says the study’s lead author, Ruben Meerman, a physicist and Australian TV science presenter. In their paper, published in the British Medical Journal today, the authors show that losing 10 kilograms of fat requires 29 kilograms of oxygen to be inhaled and that this metabolic process produces 28 kilograms of carbon dioxide and 11 kilograms of water. Mr Meerman became interested in the biochemistry of weight loss through personal experience. “I lost 15 kilograms in 2013 and simply wanted to know where those kilograms were going. After a self-directed, crash course in biochemistry, I stumbled onto this amazing result,” he says. “With a worldwide obesity crisis occurring, we should all know the answer to the simple question of where the fat goes. The fact that almost nobody could answer it took me by surprise, but it was only when I showed Andrew my calculations that we both realised how poorly this topic is being taught.” The authors met when Mr Meerman interviewed Professor Brown in a story about the science of weight loss for the Catalyst science program on ABC TV in March this year. “Ruben’s novel approach to the biochemistry of weight loss was to trace every atom in the fat being lost and, as far as I am aware, his results are completely new to the field,” says Professor Brown. “He has also exposed a completely unexpected black hole in the understanding of weight loss amongst the general public and health professionals alike.” If you follow the atoms in 10 kilograms of fat as they are ‘lost’, 8.4 of those kilograms are exhaled as carbon dioxide through the lungs. The remaining 1.6 kilograms becomes water, which may be excreted in urine, faeces, sweat, breath, tears and other bodily fluids, the authors report.“None of this is obvious to people because the carbon dioxide gas we exhale is invisible,” says Mr Meerman. More than 50 per cent of the 150 doctors, dieticians and personal trainers who were surveyed thought the fat was converted to energy or heat. “This violates the Law of Conservation of Mass. We suspect this misconception is caused by the energy in/energy out mantra surrounding weight loss,” says Mr Meerman. Some respondents thought the metabolites of fat were excreted in faeces or converted to muscle. “The misconceptions we have encountered reveal surprising unfamiliarity about basic aspects of how the human body works,” the authors say. One of the most frequently asked questions the authors have encountered is whether simply breathing more can cause weight loss. The answer is no. Breathing more than required by a person’s metabolic rate leads to hyperventilation, which can result in dizziness, palpitations and loss of consciousness. The second most frequently asked question is whether weight loss can cause global warming. “This reveals troubling misconceptions about global warming which is caused by unlocking the ancient carbon atoms trapped underground in fossilised organisms. The carbon atoms human beings exhale are returning to the atmosphere after just a few months or years trapped in food that was made by a plant,” says Mr Meerman, who also presents the science of climate change in high schools around Australia. Mr Meerman and Professor Brown recommend that these basic concepts be included in secondary school curricula and university biochemistry courses to correct widespread misconceptions about weight loss among lay people and health professionals.

    Hi James, I just assumed it went down the loo like all waste!

    This is a wind-up, right? That some doctors didn’t know this? This is all covered by ‘O’ level physics and biology.

    Oh Wow, that is SO interesting. I did not know that. I DID think that the fat was somehow “burnt” as it was converted to “energy”. Wow.

    Not sure your statement about drs not knowing is correct, James, but agree it is not widely shared with general populace. As a nurse I did ‘sort’ve’ know this, but hadn’t really considered it in relation to weight loss(as the by-products of all metabolism are intricately spread over the excretory systems, depending on their composite etc). But it does gel (though I’m foggy how) with the effects of sleep apnoea on weight gain (for one instance, and related to all our goals on this forum).

    It is known that prolonged apnoea patterns in sleep interfere with (to put it simply) the interaction of electrolytes and blood gasses in the body. This means the oxygen and carbon dioxide balances are out of kilter, or basically, your factory (liver,lungs etc)isn’t processing in the background properly while you sleep. Backlogs occur, rubbish that should go to direct elimination points gets dumped by the roadside (your belly hips etc.) Bingo you gain weight in your sleep! Not fair!

    But though I am giggling at the scientific ineptitude of my explanation (so don’t mind if you are)I have spent many years decoding medical jargon for my patients and the upshot of it all is: Maintenance of you airway during sleep is essential to weight control. Sleep itself is essential. If you then consider the exhalation of fat fumes for this dedicated period of time, (when other activities aren’t vying for the energy the liver gives to digestion while you sleep) then you will believe me when I state sleep is important, and the QUALITY of sleep even more so(you need to keep the road open for the dump trucks, like).

    Please see your dr to discuss management of sleep apnoea if you know you have it. or even if your partner complains of your snoring (it means you have periods of time when you are not breathing properly = Apnoea) IT IS FIXABLE AND YOUR LIFE WILL CHANGE WHEN YOU FIX IT. PLUS,(even tho skinny people are also prone to apnoea and it comes down to individual metabolism) if you gain weight due to apnoea YOU WILL NEVER LOSE THE WEIGHT IF YOU DON’T FIX IT. I know because I have it. and got it fixed. am now hoping to fix the weight gain. happy to share details if any require more info. Cheers!

    PS. was a very interesting post though, James. Thank You.

    I agree with the principle of conservation of mass, that’s just physics (see you med students should have done that as well!). So what happens in low carb diets when they say ketones are produced when fat is being “burned”? It suggests to me that there is an overall effect. Maybe some is burned and produces H2O + CO2, and some is removed in the form of ketones and excreted if dietary ketosis is present.

    In the case of calorie restriction without necessarily restricting carbs as in 5:2, is it all down to thermodynamics only? I.e. it all goes in water and carbon dioxide, or is it that in any situation where the glycogen is being reduced however produced that we get some ketosis as well even in 5:2? Insulin lays it on, what’s taking it off?

    I have done low carb before and 5:2 and I can tell you that in my opinion there is something hormonal going on as well and it is stronger the first time you do it. In other words I have found that as you do more and more diet regimes, the less they effective they seem to be. Now why is that? If there is some additional hormonal effect (that encourages the ketosis effect) is it possible that with time your body says hey I’ve seen this famine situation before and I am going to slow this weight loss down? Does my body know a way to reduce it’s energy requirements? I have heard people shoot down this “adaptation theory” before but consider this: does science know what every part of our dna is for and what gets switched on and off in emergency situations? We already know IGF-1 reduces so what else is going on?

    If you look purely at thermodynamics (the energy balance), in 5:2 you see that normally an average male would consume say 7 x 2,500 kcal per week which is 17,500 per week (women 14,000). When doing 5:2 you would consume only 13,700 (11,000 for women) which would amount to a reduction per week of 3,800kcal (3,000kcal for women) which equates to 543g fat (429g) lost per week. That’s about 62lb a year (49lb for women). Note 1g fat is about 7kcal.

    Other factors also come into play: residual growth hormones in food (are they significant?), your thyroid performance, other hormone levels from your organs (adrenal, pancreas, spleen etc.), how much exercise and muscle build/retention you have. Remember that it’s no good losing weight if it’s your muscle – you need muscle to burn off your food energy. That’s what food’s for believe it or not! That’s why nobody has the whole thing completely worked out!

    My tips (at your own risk!): cut down on the total amount of food you eat, obviuosly. Keep off the red and processed meat (some say it lowers LDL – it did mine). Eat fish – in moderation. Don’t overeat on dairy. Eat loads and loads of veg. Keep off the cooked fruit juices and eat moderate amounts of lower sugar fruit instead, e.g. berry fruits. If you don’t believe me check out the latest info on fructose versus liver health and you are in for a shock (you will look at that carton of orange juice in the fridge in a different way I assure you). Moderation is the key and staying active. We have always known what to do, we just didn’t want to do it because we were hijacked by the food industry to consume ever more. If you have elderly parents, chances are they are slimmer than the average. They did not go through what we have been bombarded with by the food industry and back then food was simpler (and not stuffed full of sugar). You have to look after yourself!

    Some interesting posts on this subject. Not some thing most people have ever thought about.

    Hi Stinger and welcome:

    Something to think about – the longest, documented medically supervised water fast (no food/calories, solid or liquid, of any kind) was for 54 weeks, three days. The man lost 256 pounds in that time period, came out weighing 180 pounds and never felt better. Five years later, he had gained back 10 pounds.

    The body stores what it needs to survive. And what it stores is fat and protein – except for a very short term supply of carbs (three or four days worth) in the form of glucose and glycogen That should tell people what is most important for their long term health and survival.

    As for the food industry, it just went along with what the government and the doctors were preaching – that fat was bad and carbs were good. Now that the governments and doctors are changing their ‘message’, I notice the food industry selling more foods higher in fat and protein and lower in carbs.

    Chicken and egg thing, I guess.

    Here are some tips on 5:2: https://thefastdiet.co.uk/forums/topic/the-basics-for-newbies-your-questions-answered/

    Good Luck!

    Agree, simcoeluv, our food supply is pretty much evolved by supply and demand (at least in the well healed societies) we have been like spoiled kids in a lolly shop. One can’t really blame opportunists for supplying what sells. It all comes back to self discipline. Yuck! WHY must everything ‘good’ for one involve sacrifice of opulent luxuries! (like chocolate) doncha’ just hate life lessons?

    Thanks simcoeluv for your comments. Just one question regarding the guy who lost 256lb. Did he take vitamin supplementation? I would have thought that would be essential because he would have had a serious lack of C and D as a minimum.

    Actually I did do a stint at 5:2 when Michael first brought out his tv program. Prior to that I had tried atkins years and years before (the missus and I lost more than 50lbs on that each – all came back, in fact it just stopped working despite following it strictly hence my above post). A family tragedy stopped me doing 5:2 middle of last year (brother passed and then my mother was in hospital), but now I have gotten back on the 5:2 and already since this week I am about 7lb lighter which 50% is probably water. I have a fat% scale but I need a more accurate device to measure this with confidence. My doc seems fascinated by the various graphs of weight versus fat and bp etc.

    To all: keep battling on, Rome was not built in a day!

    Hi Stinger:

    I don’t know. However, Vitamin D is manufactured by the cholesterol in the body (with sunlight). Seems cholesterol is good for something!

    If I remember rightly, this fellow who fasted for over a year was in a hospital in Britain in mid 20th century so he probably received vitamin supplements.

    Regarding measuring accurately your percentage of fat–good luck with that. I looked into that and it turns out to be a very complex problem. The “bod pod” device that you see on the Horizon show has serious limitations and often gives spurious results. They work better in research where multiple measurements across multiple people are made rather than trying to accurately diagnose a single individual. Decent individual accuracy requires multiple different (and expensive) tests done near the same time. If you went to the trouble and expense, then you could calibrate your scale and possibly have reasonable data on your body’s absolute fat percentage. From what I’ve read, your scale should give you a reasonably accurate picture of the change in fat percentage if you’re careful to measure the same way every time.

    Hi Stinger.
    A DEXA scan will show you your percentage of body fat etc accurately.
    Price depends on where you are and the health system your country has.
    Good luck.

    Dlrosebury, yes hes must have had a full vitamin regime otherwise what hospital would have done it.

    I think the point is that we just need to keep focussed.. keep at it and at it. Eat smart, exercise smart, stay smart, stick around. God bless all.

    Hi James, well done on posting Ruben Meerman’s comments. This proves that weightloss is that simple, unless of course you have mitochondrial disease.

    People love keeping their bank balance in the black, and how much gas the car needs when at the pump, but do they check their calorie intake when filling up with food and drinks?…No! People do not look after themselves, and believe in fad diets.

    Science wins every time, people ignore science….sadly!

    Regarding the breakdown of fats, a process known as Lipolysis, this is the opposite of ‘fat storage’, and is how your fat cells are opened and used during fasts.


    I can personally say that mine went from fat to muscle. I have worked very hard to make this happen. I am 52 and have lost around 4% fat in 2 months of 5.2, But I have lost very little weight overall 5 pounds. My wife laughed when I started fasted 2 days a week. She doesn’t anymore.

    Weight loss doesn’t increase absolute lean mass. Although it will relatively increase lean mass. The only way to increase lean mass in absolute terms is by exercise, with an emphasis on resistance training.

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