If no carbs are available, our bodies start burning fat as a primary fuel source and producing ketones in the liver, which the body can turn into energy, as previously mentioned. Here David Grainger, Forbes.com, reflects on his experience with the science behind ketogenic diets:

 

“The internet is abuzz with anecdotes telling of the amazing benefits of a ketogenic (or “keto”) diet. Nothing new there, then, as every year is marked by the rise and fall of a new diet fad – most amplified by the social media echo-chamber but with little to commend them.

This time, though, it caught my attention.  Not just because I am a modestly overweight 52 year old whose love for food and drink is slightly stronger than my desire to be skinny, and as a result someone who has been on a diet every January for at least 20 years and now knows he needs he miracle.  But because of the science behind it.

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For a start, I first began reading about ketogenic diets thanks to Ethan Weiss, M.D., a prominent UCSF cardiologist on Twitter, whose scientific acumen I respect.  If he believes in the benefits of ketosis, then I should definitely look a little closer.  After 20 years of January diets, my own experience suggested that nothing made any difference: you only lost weight if you took in less calories than you used, and if you took in less calories than you used then you were hungry. Simple as that.  Could it be that a ketogenic diet really was different?

Well, the principle makes sense.  Bizarrely named “ketone bodies” are actually molecules that act as the body’s natural back-up fuel supply when glucose is scarce.  Normally, we only enter ketosis (where ketone bodies accumulate in the blood) when we starve ourselves – not just overnight or by missing a meal, but for several days at time.  Our metabolism then switches to fat-burning, and converts stored fat molecules into ketone bodies that can power our muscles and brain because the glucose has run out. Being in ketosis, then, does sound like a great way to burn off the fat.  On the other hand, not eating for days doesn't sound much fun.

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But it turns out you don't need to starve yourself to get into ketosis. All you need to do is remove carbohydrate from the diet (not just refined carbs, such as sucrose or high fructose corn syrup, but all carbs, including complex carbs and starches too). Once the body has no source of glucose, it has to switch to ketosis because the brain needs either glucose or ketone bodies to survive. So no matter how much protein or fat you eat, the body still has to break down fat to ketone bodies to keep you going.

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A ketogenic diet, then, is any diet that switches your metabolism to ketosis. And the ones doing the rounds at the moment aren’t the first or the only diets to do that. It is several decades since the Atkins Diet rose to prominence – and I witnessed first-hand the weight loss some friends achieved on Atkins. The Atkins diet is a ketogenic diet, because it removes carbs from the diet and replaces them with protein. The surprising finding was that Atkins followers discovered they were much less hungry than they expected, suggesting that calories from protein made you feel more satisfied for longer. Feeling fuller translates to willingly eating less, and in the end impressive weight loss.

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In dieting, though, there is no such thing as a free lunch (or so I thought). Adherence to the Atkins diet has side-effects, and most worrying is the impact on nitrogen balance from taking in so much protein. There is a very real risk of dehydration, and over the longer term, kidney stones from the need to excrete so much excess nitrogen as urea.

So what about the 21st century version? Keto today replaces the carbs with fats rather than protein. A typical Atkins regimen had 75% of calories from protein, 25% from fat and <5% from carbs. By contrast, today’s keto diets advocate 75% of calories from fat, 25% from protein and <5% from carbs. As protein intake isn’t changed from a typical “balanced” diet, any side-effects from nitrogen imbalance are neatly side-stepped.

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But what about all that fat? Surely that's got to be unhealthy? Well, no. Most instructive are the lipid profiles of Antarctic explorers who have crossed the continent on foot, dragging their own food on sledges. That's only possible with food that has the highest possible calorie to weight ratio – which means eating essentially nothing but butter. And after months on an all-butter diet the level of LDL-cholesterol (often called “bad cholesterol”) actually declines significantly. That isn’t as surprising as it sounds – while in ketosis, fats are being moved from stores towards the liver (where the ketone bodies are made) and that's the job of HDL-cholesterol. LDL-cholesterol typically moves excess fat from the liver to the stores in the rest of the body (hence in the opposite direction). So in ketosis, you would expect a lipid profile normally considered healthier (higher HDL and lower LDL) no matter how much fat was being consumed.

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But if the benefits of Atkins on weight came from the reduced hunger thanks to the sustaining properties of protein, then you shouldn't get that unless you bulk up the protein component of the diet. It turns out, though, that the reduced hunger results from the state of ketosis itself. How you achieve it doesn't really matter.

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So the science stacks up – theoretically, at least, I couldn't find a flaw in the modern ketogenic diet. So I gave it a try in place of my usual “low-everything” calorie restricted January diet.”

Exercise is considered a way to stay healthy and extend life. The Body Reboot book reveals how a low carb, high fat diet can improve health, as previously mentioned.

 

Read More … Article Source: https://www.forbes.com/sites/davidgrainger/2019/02/01/the-science-behind-ketogenic-diets-or-why-we-get-fat-and-what-to-do-about-it/#10cd70143420

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