I am still not really understanding the science

(Ally) #1

I am still not totally understanding the science behind Keto. When I try to explain to the doubters about a Keto diet I get stuck at the bit about why we have to eat fat. If we are trying to get our bodies to use our own body fat to break down into ketones for our energy source then why do we still need to eat fat? Is it because if we eat anything other than fat then, carbs, sugar or protein then the body will take that first and break it down onto glucose for fuel and won’t bother breaking down our body fat in to ketones? I watched a TV show the other night ( a controlled 800 cal a day experiment on 5 people to see if they could reverse type 2 diabetes with an almost starvation diet) the doctor said that because they were consuming such a low amount of calories then they were in ketosis. This was all done by nutritional shakes and there was no mention of eating lots of fat. When they came off the shakes they were to remain on a very low cal diet and try to stay in Ketosis but they were told to eat food that is not dense in calories and that meant not eating much fat.
Is a Keto diet about eating lots of fat or about forcing your body into ketosis by eating few calories…will the results be any different. I really don’t see how eating way over a calorie deficit is going to help you loose weight just because you are eating lots of fat. Please can someone explain it to me.

(LeeAnn Brooks) #2

Tell them it’s about keeping insulin from spiking, which causes weight gain.
Carbs spike insulin the highest.
Protein does too, but not as much as carbs.
Fat only has a minimal insulin spike.

It’s the insulin that’s making us fat.
And we gotta eat something, so fat it is.

(Solomom A) #3
  1. Calorie restriction (CR) is not easy but it works. It’s been around forever and we all know how complaint we have been.

  2. The Ketogenic diet provides all that we want from the CR without the hunger. Some restrict calories automatically on Keto, but not to the same degree as on CR but with greater compliance because of the lack of hunger. Keto lowers your insulin to get all the metabolic benefits you desire.

  3. Sarah Hallberg has an excellent Tedtalk video on youtube explaining the science.

(Adam Kirby) #4

One misconception is that you have to eat “lots” of fat on keto. You eat enough fat to be satiated. Starvation will definitely put you in ketosis, as will keeping your carbs low (hence the phrase “nutritional ketosis”).

(LeeAnn Brooks) #5

Well, it should still be the majority of your macros.


Your body can only use two forms of energy, sugar and fat (ketones are a metabolite of fat).

If you cut calories, your metabolism drops, so you can’t do that consistently. (Fasting is a different story.) If you meet your calorie needs with carbs, your insulin increases, and insulin is a storage hormone. It will stop the usage of fat as fuel and will cause storage.

If you meet your calorie needs with fat, then insulin stays low and your body shifts over time to preferentially burning fat as fuel. Your metabolic rate isn’t affected, and your energy doesn’t bounce around as your blood glucose goes up and down (as it would with sugar burning). When the fat you’ve eaten is used up, your body goes looking into your fat stores, vs. becoming more sluggish.

Excess ketones (those metabolites of fat) get peed out or breathed out. Your internal fat even becomes metabolically active, instead of sitting around doing nothing. Great talk by Benjamin Bikman on this topic:

(Adam Kirby) #7

Of course, but as an absolute amount I’d argue you don’t eat much more fat than people on the standard western diet.

(karen) #8

Part of why we utilize fat the way we do in keto is because of insulin resistance. As I understand it, insulin resistance means the body has to produce More insulin to get glucose managed. More insulin = even more fat storage. So not only are we trying to limit carbs to limit the amount of glucose in our bodies, after years of excess carbage we have these unnaturally large, long insulin spikes going on every time we carb ‘load’; fat is a choice that improves both the glucose content and the insulin level in our blood.

There is another idea out there, one I’m trying to find more info about. It’s got to do with the kind of fat we’ve been SAD-ly eating. Cell membranes are about 50-50% fat and protein, and apparently the “industrial oil” (processed vegetable oil) we’ve been fed will be used by the body to build cell membranes, but it creates membranes that don’t function properly. I’m not sure what “not properly” means, I’m wondering if that has something to do with insulin resistant membranes, or possibly the difficulty in getting cells to release fat easily / timely … in any event, it’s not just any old fat we’re after in a keto diet, it’s natural fat from animals and easy-accessed plant fats like avocados, olives, coconuts, nuts.

(So, it’s just a theory, but for me, I’m hoping this hefty supply of good fat helps to build healthier cell membranes that react in a robust and timely manner. … I know this is just fantasy, but when I imagine a cell wall built with a substance that required heat, pressure and chemicals to create, I imagine something that’s like wads of gum, vs. a fat that easily changes from solid to liquid, sort of a magic mirror responding to a tiny change in temperature or a chemical key … it’s goofy but I don’t see the harm in positive visualization, anyway …

(Bacon is the new bacon) #9

Karen, the dangerous fats are the polyunsaturated fatty acids in seed oils. Firstly, some of the compounds themselves occur nowhere else in nature, and then using these oils to fry with creates oxidated compounds that are completely unknown in nature, and we don’t understand what they are or how they behave in the body. (Mary Enig was one of the researchers who first warned of the effect of trans fats and PUFA’s in the diet, and there is a reasonably decent lecture by the former president of the Weston A. Price Foundation that explains some of Enig’s research.)

Cell walls in animals are constructed of cholesterol and other fats (in plants, the main constituent is cellulose), so if there are fats in our diet that we didn’t evolve to cope with, and they are replacing the usual fats in our cell walls, that is of concern, because there is some research to indicate that cells with those replacement fats can’t properly absorb or properly keep out the things they need to absorb or keep out. We don’t really know enough about this yet, from what I’ve read, but it is certainly concerning. Nina Teicholz goes into this in one of the later chapters of The Big Fat Surprise.

(karen) #10

yep, PUFAs and seed oils, but I’m also highly suspicious of corn oil and soybean oil, basically anything heat and hexane treated. If my body couldn’t extract fat molecules from something, I’m questioning whether it’s an appropriate fat to use to build my body’s cells. So far I’m giving olive oil a free pass, I can squash the oil out of them, but I’m open to new info.

. Exactly. Like I said, I envision a wall made of wads of gum where there should be little pools of easily penetrable fat.

(Robert Morris) #11

Really quite a large topic…I think we are all learning the science of keto. Hopefully I can shed some light with some nuggets I’ve found. Everything we eat invokes an insulin response (to some extent). Insulin is a hormone that shuts down the burning of body fat and ramps up the storage of fat into our fat cells. We have to have ‘some’ insulin working in our system, we just want it to work normally, not over heated in the case of type 2 diabetes. The ketogenic diet drastically helps to keep our insulin production and use at that normal level. Our bodies can burn two major types of fuel (we call them Macros) which are carbs and fat. There are separate systems and processes set up in the body to deal with each type of fuel. Carbs ramp up insulin production and thus fat storage and other problems. When our body burns fat, it needs a lot less insulin to process it and…fat is a much better fuel for all the cells in our body. So, what about ketosis and why is it important? Our body enters ketosis after we’ve used up most of the carbs in our system (from a meal, or from ‘glycogen’ or reserve carbs our body stores up), At this moment, the body say “Hey, there’s no more carbs, gotta keep going, so switch to the other fuel…fat”. Now the body cranks up the keto engine to burn fat. If there is a lot of fat being supplied in the diet, it will use that first. If not, and there is no other food coming in (like when we are asleep or fasting), it will pull what it needs from our body fat…this is when it makes the most ‘ketones’…ketones are a form of medium sized fat molecules that work very well in feeding our brains. Ketones really light up the brain…that’s why folks on a fast feel really good after they get past the hunger stage. So, why eat fat and avoid most carbs? Mainly insulin. You can’t just add a lot of fat to a regular diet…because most standard diets have a lot of carbs and that will invoke a lot of insulin which will just store the fat you’re eating rather than use it for fuel. What we have to do then is to reduce our carbs (drastically in my case) and increase good healthy fats. Making this ‘a way of life’, not a temporary thing, will cause your body to shift all of its major processes over from carb burning to fat burning…this is what they call being ‘fat adapted’.


Just from a science standpoint, the production of ATP alone supports fat as a good method of losing weight.

ATP is essentially like money or gas for reactions in the body, like skeletal muscle movements.

When you eat food fat has the most energy per gram, however, the amount of energy.expended.to produce something useful is also great, unlike carbs.

So when creating ATP from fat you would only get a small handful of return, where as carbs you would get a pick up trucks worth. Sry I’m trying to boil down the science for anyone to understand.

If you consume less than your basal metabolic amount of calories, your body will grind your matabalism to a halt because if you are not eating, you are not creating as many chemical reactions once you run out of glucose and stored glycogen from the liver. So without those you are not creating as much heat and your.fat serves as a blanket, so it wouldn’t make much sense survival wise for your body to eat it’s blanket. Instead it eats your muscles. So to avoid this we eat fat. The constant intake of fat will yield little energy for great effort, so the body will substitute in stored fat from the body because the body isn’t in fear of starvation or freezing.

(Ilana Rose) #13

I’d like to see this science. It’s not what I’ve found at all.

“…the value for the ratio of the energy content of fat to that of carbohydrate is almost identical to the ratio of the yield of ATP per gram of palmitic acid oxidised, compared with that of glucose.”


I’m also not sure where this is coming from. The body absolutely consumes fat stores preferencially to muscle fibre. There is a small uptick in lean mass consumption for a few hours after glycogen is exhausted and then it declines while fat catabolism increases.

(Scott) #14

You don’t have to force fat but you don’t have to fear it either. For years nutritional guidelines told us to reduce fats, eliminate healthy (saturated) fats, increase unhealthy fats (corn, canola). They were just plain wrong and are having trouble reversing themselves. To others they see fat on your plate as bad and bread as healthy. It will take a lot of time and education to move this opinion from its current position.


For one thing, if all you ate was 20g carbs and say 100g protein you would be at a severe caloric deficit on a daily basis and likely crash your metabloism unless you had maybe an extra 50 pounds of bodyfat to draw on.

For all things related to calorie restriction, SEE THIS TOPIC.


Fat is the thing that is used first survival-wise. It would make no sense to catabolize muscle tissue when there is abundant energy stores ready to us as long as insulin is low enough.

(Bacon is the new bacon) #17

ATP is the fuel for absolutely everthing the cells in your body do.

While it is true that fat is the most energy-dense of the three macros, the cost of metabolising it, also known as its “thermic effect,” is the same as that of carbohydrate. It is protein that costs extra to metabolise, and this is because, under normal circumstances, we do not want to be metabolising our muscles.

The production of ketone bodies from fatty acids in the liver, and the complete metabolism of fatty acids in muscle, yields a great deal of energy from the raw fatty acid. This is why the muscles adapt to metabolising fat, not just ketone bodies, on a low-carb diet, and why the organs that can avail themselves of ketone bodies seem to run better on ketones than on glucose.

You are correct that restricting caloric intake causes a famine reaction that slows the metabolism, even in the context of a low-carbohydrate diet. In a situation of abundance, the metabolism ramps back up again, and the cells of our adipose tissue uncouple their mitochondria from their metabolic needs, allowing the mitochondria to actually waste energy. (Muscle-cell mitochondria do not become uncoupled, because there is no evolutionary advantage to inefficient metabolism in muscle tissue. Quite the reverse, in fact.)

In famine conditions, the muscle is broken down in preference to stored fat, but only up to a point. Past that point, the body gives in and starts mobilizing the fat reserves (this is the ketosis of fasting). It’s a delicate balance between preserving muscle function and trying to hang on to reserves long enough to get through the famine–a balance that the human body has spent some two million years perfecting. (This is why restricting calories is such a bad idea.) The survivors of the Nazi concentration camps were by and large very far along the process of starvation by the time they were rescued, as evidenced by their obvious lack of body fat. A number of them didn’t survive rescue, because they were so far gone.

In situations of abundance, the body ramps up the metabolism and is willing to release excess stored fat, and it is willing to fuel the metabolism from the fat store during times of fasting (fasting is a very different signal from calorie restriction). I suppose that the evolutionary logic is that, once the mammoth meat is all gone, the hunters need their strength to go out and bring back another mammoth, so a cycle of feasting and fasting signals good times to the body. There is little evolutionary advantage for a hunter to get too fat, which is why, when on a low-carb diet, the body seems willing to part with its excess fat.

The key to signaling properly to the body is the notion of eating to satiety. Yes, if there is excess fat to dispose of, we will eat at a caloric deficit, but not intentionally, and it is the body making the decision, not the brain. It is very hard to out-think two million years of evolution.


Sry I’m at school I can’t really elaborate right now but no, your body won’t eat it’s fat first. You will break down the muscles for the amino acids before depleting your organs insulation.

Will you use any fat? Sure but starving yourself doesn’t work for weight loss because your matabalism essentially shuts down and you stop producing as much heat as a result thus prompting the wasting of muscles in an attempt to keep you alive without losing heat


Ketogenic diets are muscle sparing and even increase human growth hormone. Now you take food away from someone not already fat adapted, and you will see short term lean tissue loss. How much of that is the glycogen stores being depleted and how much is muscle fiber would take some diagnostic testing.

(Bacon is the new bacon) #20

As Robert Heinlein put it, “Even when you raise the thermostat, you are just trying to find a more comfortable rate of losing heat.”

Every chemical reaction releases heat energy; the body’s main challenge is to find a way of maintaining body temperature at the level that is most effective for the reactions we have evolved to need most. Microbes that get into the body have a temperature at which their reactions run most efficiently, too, which is why fever is such an efficient instrument in healing from an infection.