This page on the British Nutrition Foundation website was mentioned here recently. It encapsulates almost every incorrect belief in mainstream nutrition, and I thought it would be instructive to pull it apart:
I do realise, incidentally, that I come across as a bit of a know-it-all when I do these dissections of mainstream nutrition policy. Physiology is a complex subject and a lot of what goes on inside our bodies is still unknown - and perhaps unknowable. Since even very-qualified, immensely clever people don't know everything, it follows that I know even less. But I probably know more than the average nutritionist - as, I suspect, do many of the members here - because I make the effort to find out how things actually work, as opposed to just making stuff up and attaching some sciency-sounding words to it. With that proviso, here's my critique:
Fat contains 9 kcal (37 kJ) per gram ...
The total energy content of a food can be found by burning it and measuring how much heat is released.
The idea that our bodies derive a constant amount of energy from the macronutrients we eat, equivalent to their heat of combustion, is fundamentally wrong. Chemical energy is an inherent property of the bonds that hold a compound together, so the amount of energy released from any given compound is a function of the reaction(s) performed upon it. While the foods that we eat ultimately end up as carbon dioxide and water, and all of its potential energy ends up as heat, this does not mean that our food has been "burned" as it would have been in a heat engine. Food goes through a whole bunch of conversions, and storage and recovery operations, each reaction having a certain efficiency associated with it.
As a rough handwaving approximation, our bodies extract about 20% of the chemical potential energy from our foods as useful work, the remainder being lost directly as heat. Interestingly, this efficiency figure is much, much higher than it would be for a heat engine operating at body temperature (it'd be 3-4% at best). In other words, "the laws of thermodynamics" do not apply to human beings, whatever the nutritionists might think.
TL;DR: it is broadly true that our bodies can extract more useful energy from a gram of fat than from a gram of carbohydrate, but the statement that "a gram of fat contains 9kCal" is misleading, because we do not eat in order to generate heat. Our bodies use some fraction of food-energy to perform work .. but we have no way of knowing what that amount is, or how efficiently it can be extracted from our food. The idea that we can calculate how much food we should be eating is therefore false.
Basing your diet on foods which are lower in calories (or have a lower energy density), and eating foods which are high in calories (or have a higher energy density) less often and in small amounts, can help to control you overall calorie intake.
There is no obvious reason why this should be true. They just made that up. It could only be true if human bodies were incapable of regulating their energy intake and expenditure. Since our bodies actually have extremely sophisticated methods for maintaining both energy balance and mass balance, we would expect that people who eat larger amounts of fat (relative to carbohydrates) would simply eat less. And experimentally, we know that this is exactly what happens ... at least, in the absence of food-science modifications which are designed to mess with one's appetite.
Carbohydrate is the most important source of energy for the body because it is the main fuel for both your muscles and brain.
No, it isn't. There is nothing inside your body that can use carbohydrates for energy. Certainly, most of your organs can use glucose, and a few of them need a certain minimum amount of it. But "glucose" is not the same thing as "carbohydrates". A fat molecule, for example, will be broken down into three fatty acids and one glycerol molecule; the former can be burned directly or indirectly by almost all of your body's cells, and the latter is generally converted to glucose (by a short and elegant chain of reactions) for those few systems that need it.
At low power output, your muscles actually rely mostly (80%+) on fatty acids for fuel, conserving glycogen/glucose for bursts of high-power activity - the implication is that sedentary adults have very little need for carbohydrates, and would be better off eating dietary fats. Your heart muscle uses fatty acids almost exclusively, and ketones to a lesser extent. It will only use glucose if there's a glut of it relative to fatty acids (that is, while a carb-heavy meal is being digested).
Your brain does need a little glucose, but the amount is considerably less than nutritionists assert. It is physically impossible to deprive your brain of glucose.
Your weight depends on the balance between how much energy you consume from food and drinks, and the total amount of energy that is used by your body. When you eat or drink more energy than you use, you put on weight; if you consume less energy from your diet than you use, you lose weight
There are at least three assumptions here which are demonstrably wrong:
a) Your body does not, or cannot, regulate its own energy balance
b) "Weight" is the same thing as "bodyfat"
c) Bodyfat is merely a dumping ground for excess energy and has no other physiological function
Most fat people are not actually getting fatter, but just "maintaining" at an unhealthy bodyfat ratio. My cousin's wife has been overweight for as long as I've known her (a very long time), but she's been consistently overweight. She's not ballooning. If the nutritionists are correct, she's in caloric balance - and why shouldn't she be? All human bodies are, most of the time. So the question arises: why is she maintaining so much bodyfat? The nutritionists don't know. Their theory doesn't offer any explanation.
The correct way of phrasing the original statement is as follows:
If you are gaining weight, you are eating more than you are expending; if you are losing weight, you are eating less than you are expending.
This is a completely uninteresting statement, with no earth-shattering implications. Why? Because energy-in and energy-out are variables, not constants. Your body can adjust energy-in (via appetite) and energy-out (in a whole bunch of complex ways). Deliberately eating less than your appetite demands is something that you cannot maintain for more than a few weeks or months, in most cases ... and it won't help you anyway. All that happens is that your body will dial back its metabolic rate to match the caloric restriction - which is precisely what you'd expect from a homeostatic system. Of the people who attempt to lose weight this way, 95%+ of them fail within 3 years.
The point here is that bodyfat has a purpose: to store excess food energy, and release it as needed (ie., when you're not eating). In fact, since humans aren't eating all the time, it's clear that "carbohydrates are the main fuel for your body" is incorrect. The average body is running mostly on stored glycogen and fat. Here's the conundrum: why do some bodies store more fat than they (apparently) need? The nutritionists don't know, but they confidently assert that the solution is:
eat less, move more!
There is now a vast mountain of evidence - not to mention personal experience - that shows this doesn't work. And yet they keep repeating it. Why? I can think of only three possible explanations:
1) The nutritionists simply don't have enough scientific background to understand how flawed their theories are.
2) The nutritionists are so attached to their theories that they're unwilling to discard them in the face of overwhelming disproof.
3) The nutritionists are under financial or political pressure to keep this game of musical chairs going for as long as possible, because it's not going to look pretty when the music stops.
So which is it, BNF? Do you have an alternative explanation? I've emailed to you ask. Feel free to post your reply here.
Written by
TheAwfulToad
Ambassador
To view profiles and participate in discussions please or .
Well said. I would be interested to see what the BNF response is (if they do actually respond!)
Luckily the worm is beginning to turn and people are realising that the information we have been given in the past was a load of 💩. So many people have been made to feel a failure because of their inability to lose weight despite doing everything that the diet industry has said they should do.
One of the funniest things I heard was on a documentary about Weightwatchers. One of the senior employees said “weightwatchers obviously works otherwise people wouldn’t keep coming back to us” 🤔😂😂
Keep on waving that LCHF banner TheAwfulToad , we are right behind you. 😃
Thanks for the encouragement, although I'll be very surprised if they reply!
Weightwatchers, eh. It's hard to tell if they genuinely believe that, or if they're just being completely cynical.
I will tell you what I think TheAwfulToad , I do not see you as a know all but someone who has thought things through practices what they preach and I think that you and others on here could well be ahead of the curve. And I for one am interested in what you say. 😊
It is fascinating. The bit that the body adapts its energy expenditure sounds just right. Think about someone with an eating disorder. When such a person starts restricting their food intake they start losing weight. Eventually they get to a point when the weight loss decreases as the body reduces its energy expenditure to survive. It starts shutting down the systems that are not essential for survival, like the reproductive system and so on. If you reduce the food intake any further the vital organs would start to fail and it could be fatal. That is why reducing calories by itself is counter productive, as you cannot do it indefinitely. Your body just would not accept it.
I am not sure about the calories though. If you abolish the calories, as a measure of energy, what would you replace it with? Do you have to replace it with something at all? I have to admit that I feel confused and I am not sure what to think about this.
I agree that human body cannot be compared to a heat engine, as it is much more complex. But can you completely ignore the balance between energy in and out?
What I think is that calories matter, but not all calories are equal. So to lose weight you need to create some energy deficit. I think the question with energy deficit can be addressed in two different ways:
You can do it buy counting calories and eat whatever you like - potatoes, pizza, cake and so on, as long as it within your calorie allowance. If you read posts on the weight loss forum on HU, some people are happy to do it this way. Whether is sustainable as a life style, I am not sure.
The other way to do it, is to ignore the calories and be mindful of what you eat and when you eat it - hence LCHF. You substitute starchy carbs and refined sugar with fats and protein. Insulin levels would not spike, you would feel fuller for longer and would not eat constantly (hence not excess calories intake). As a result you would lose weight.
For your fundamental question: why nutritionists still advocate "eat less move more" - I think, it is because the majority of them are not really very good. You can call yourself a "nutritionist" after completing, shall we say, a month-long online course.
Vested interests also matter. If the food industry spend huge amount of money to create "irresistibly" tasty products, they need to make us buy it, so they do not really care whether we are fat and sick as long as we keep consuming their products. That is why diet drinks and low fat products are labelled "healthy".
Well said esp last paragraph .... we've had half joking discussions on here before about what the "new" trends will be .. "VEGAN!!!!!!" is obviously one! Think it will be a while (if ever) before we see "LOW CARB!!!!!" or "FULL FAT!!!!!!!!" ....... I guess we're supposed to be grateful for "SUGAR FREE!!!!!!" but ignorance is bliss on what else such things contain xx
Hi cheritorrox the vegan trend is non stop but its processed and take away vegan foods from Gregs and meatless burgers that are on trend plant based wise.
Pre-diabetes and preventing diabetes is going to be more and more prevalent in shoppers needs and wants as is preventing obesity. So I see a growing interest in an LCHF diet, fasting, fitness and eating better. 😊
If you reduce the food intake any further the vital organs would start to fail and it could be fatal. That is why reducing calories by itself is counter productive, as you cannot do it indefinitely
Quite. A body that responded in the way that the nutritionists think it should respond would soon be a dead body. 50,000 years ago it would have never survived to reproduce.
I am not sure about the calories though. If you abolish the calories, as a measure of energy, what would you replace it with?
Nutritionists tell us to measure our food calories so that we can reduce them. This is just a pseudoscientific way of saying "eat less food". But we all know what eating less food does to you. Since restricting "calories" is pointless, counting them is likewise pointless.
Your body controls how much bodyfat you carry, all by itself. It controls how much food you eat, and what happens to the energy and materials in that food. Your will, self, consciousness, or whatever you want to call it has absolutely no direct influence over any of these processes. None. You can only do two things to the control loops that manage them:
1) Let them work properly.
2) Befuddle them (by eating food unsuitable for humans, consumed over many years).
Those are your only options. The behaviour of any control loop is determined by its setpoint, and we have no access at all to our bodies' internal setpoints. Fat people are fat because they've decided upon option (2), not because they eat too much or exercise too little.
But can you completely ignore the balance between energy in and out?
Yes. The nutritionists have got the causality completely backwards. People eat less when their bodies are losing fat mass. The fat-burning is a deliberate decision by your body's internal mechanics. The lack of appetite follows naturally. Conversely, people who are packing on fat eat too much because they are packing on fat: the dysfunctional storage of energy in insulin-resistant fat inevitably means they must eat more.
So to lose weight you need to create some energy deficit.
I think focusing on the process of "weight loss" is where it all goes pearshaped. Nobody wants to "lose weight". The process is not the goal. We just want to be slim. And we want to stay slim.
Nutritionists babble on about weight loss because (a) they genuinely believe that creeping weight gain is inevitable and normal and (b) they can put forward a half-baked theory for how it works. They have no theory that explains steady-state obesity (or, for that matter, steady-state slimness).
I would like to hear a nutritionist explain why some people are slim, and some people are fat - neither losing nor gaining (at least not at any noticeable rate). In particular, I'd like to hear them explain that all-too-common scenario on the NHS group, where people on calorie controlled diets frantically report that they've gained 2lb this week, and what should they do? And then the following week they post that all is well because they've lost 2lb again. The reality is that these people are just maintaining a constant state of obesity ... on caloric restriction.
It seems to me that if you're always eating foods that demand lots of storage (processed carbs), then lots of storage is what you'll get. You will become - and remain - fat. People eating high-fat low-carb meals, on the other hand, don't need bodyfat. The energy they eat is buffered in the small intestine, bloodstream, lymphatic system, and only to a small extent in adipose tissue. Inevitably, then, their "store cupboard" will be relatively empty; it doesn't need to have anything in it because no demands are placed upon it.
You can call yourself a "nutritionist" after completing, shall we say, a month-long online course.
Indeed
so they do not really care whether we are fat and sick as long as we keep consuming their products.
Yup. Whatever does not kill us makes them stronger.
I can't tell if the nutritionists are in on this unpleasant little game, or whether they're just being played as "useful idiots".
There was a program on TV (might have been on Chanel 5) a year or two ago: "How do they stay so slim" or something like that. I remember one of the episodes with a girl that was very slim despite eating all sort of rubbish food. They followed her for a week or whatever they do in such shows. The results were really interesting. She would have for example a sausage roll. However she would have a few bites and simply chuck the rest in the bin. Than later it would be a burger - same thing. A few bites and bin the rest. A biscuit, that was it. They established that the amount of calories she was eating in a day altogether, was below of the recommended amount for an average woman. When she was hungry she ate, but her body would tell her when to stop. And she would recognise immediately she didn't need anymore food and would stop. She was not losing or gaining weight despite her unhealthy diet. So energy in and out in her case seemed to be in equilibrium. This would not work if a person is obese though, as their hormonal responses are messed up.
This would not work if a person is obese though, as their hormonal responses are messed up.
That's the bottom line, isn't it. But the nutritionists refuse to even consider that such a thing might be possible, nevermind a crucially-important factor.
"The total energy content of a FUEL can be found by burning it and measuring how much heat is released."
If you are burning fuel to generate heat - for cooking or to power a steam engine, this is true.
If you use fuel in an internal combustion engine (or a jet engine) this might not be the case.
You can measure the energy in a bale of straw this way - but the net human metabolisable energy is very different.
A steam engine needs heat, but an internal-combustion engine does not.
Mammals are different - and we need to be warm - so food energy turned into heat is not waste heat... unless we are exercising hard or in a hot environment.
eat less, move more!
At one point, I tried using my exercise bike to use up some calories. (My RMR is rubbish.) It would tell me that I'd burned, say 250 calories (unlikely, given the RMR issue). However, it made me hungry for 300 calories. You sometimes read patronising things that say you treat yourself because "you've earned it" from exercise, but in my case that was nonsense. I was disappointed to be so hungry after the exercise...
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.
loss of muscle mass over 40
LCHF, Intermittent Fasting and Calories
Shocked at weight gain