Updated: Oct 8, 2020
Are you wondering how does the keto diet work? My lab report from my Sports Nutrition class is an FAQ for all the science behind this much misunderstood diet & its benefits for sport & weight loss (and yes, there are several).
What is ketosis?
Ketone bodies (KB) are produced after several days of fasting or drastically reducing dietary carbohydrates. In that time, glucose reserves deplete to the point where they are no longer sufficient for either normal fat oxidation or to supply energy to the brain and central nervous system, and an alternate energy source is required.
This energy is supplied by ketone bodies which are generated via a process called ketogenesis that occurs primarily in the liver mitochondrial matrix.
Ketogenesis is initiated to make available energy that is stored as fatty acids. Fatty acids are enzymatically broken down in ß-oxidation to form acetyl-CoA. Under normal conditions, acetyl-CoA is further oxidized by the Krebs cycle and then the electron transport chain to produce energy. However, if the amounts of acetyl-CoA generated in fatty acid ß-oxidation excess the capabilities of the Krebs cycle it is then used to make ketone bodies.
KB are then used as an essential energy source by the brain and other tissues. KB are converted via several steps to acetyl-CoA, which can be used via the ATP-generating Krebs cycle.
What is ketosis useful for?
Ketosis may be a useful diet for athletes to improve power-to-weight ratio, compete in a favorable weight category, or achieve extreme leanness for aesthetic reasons. When practiced appropriately, it can be a sufficient and balanced diet that is safer than many common rapid weight loss methods.
Is there any documented evidence?
In taekwondo athletes, 3 weeks of a ketogenic diet (KD) improved aerobic capacity and fatigue resistance capacity and exerted positive effects on inflammatory response.
In gymnasts, a 30-day KD doesn’t impair power output, therefore could be useful for power athletes to meet weight categories while maintaining power output.
In endurance cyclists, a 4-week KD didn’t have any negative effects on aerobic performance. Off-road cyclists reported a significant increase in VO2max and improvement in lactate threshold; this may be caused by reductions in body mass and fat mass and/or a greater oxygen uptake necessary to obtain the same energy yield.
Are there different kinds of ketosis?
Physiological ketosis is an evolutionary adaptation to counter long periods of undernutrition because of unreliable food sources, leading to decreases in blood glucose and insulin, along with increases in glucagon as the body attempts to maintain physiological levels of glucose. KB levels may reach 7-8 mmol/L, without any pH change.
Pathological diabetic ketoacidosis reach KB levels in excess of 2- mmol/L, and the pH of the blood rises higher than the pH of the tissues. This drastic imbalance may lead to diabetic coma or death.
Can physiological ketosis have any benefit for diabetics?
Reducing carbohydrate levels to very low levels can activate AMPK & SIRT-1, both can have beneficial effects on glucose homeostasis and insulin action.
How does the keto diet work?
The actual mechanisms by which a KD is effective in weight loss are unknown, but the possible reasons are:
Appetite reduction: protein satiety, effects of appetite-related hormones such as ghrelin, and possibly a direct appetite blocking effectReduced lipogenesis and increased fat oxidationA reduction in respiratory quotient may indicate a greater metabolic efficiency in fat oxidationA thermic effect of proteins and increased energy usage by gluconeogenesis
Are there any negative effects to ketosis?
A KD blunts the insulin-like growth factor, reducing the possibility of gaining muscle despite energy sufficiency. All data regarding biochemical and molecular mechanisms suggest that it is very difficult to increase muscle mass and should be limited to the few days immediately before competition in bodybuilding.
Is there any muscle loss during ketosis?
The muscle- (or protein-) sparing effect occurs after a few days of ketosis when the central nervous system is supplied with glucose for energy by breaking down muscle tissue to amino acids. To avoid this, KB are produced at higher levels and provide a fat-based source of energy that spares muscle tissue. The use of KB and free fatty acids for energy slows muscle protein catabolism so the lean body mass is general well conserved.
What are the weight loss benefits of a ketogenic diet?
Because ketosis is a type of modified fasting and the specific metabolic state is quite different, the negative observations associated with common rapid weight loss methods may not apply. Short-term use of energy-sufficient KD has not been associated with any long-term health issues, and the few symptoms of fatigue and headaches disappear after a few days. Biochemical, physiological and observational studies provide good evidence that an actual KD can lead to fat loss with little or no loss of muscle mass.
It is a key misconception that the KD is unsafe because it is a high-protein, high-saturated fat diet. The key feature is energy sufficiency with a very low carbohydrate intake, compatible entirely with normal protein consumption and a rich nutrition providing full complements of micronutrients and essential macronutrients. Overall, the KD may well be one of the most intensely studied nutritional systems that exist for weight loss.
How long does it take for the body to shift into ketosis?
Approximately 7 days are required for full adaptation into physiological ketosis, but it depends on the amount of glycogen stored in your body & how long it takes to deplete.
Fatty acids are enzymatically broken down in ß-oxidation to form acetyl-CoA. Under normal conditions, acetyl-CoA is further oxidized by the Krebs cycle and then the electron transport chain to produce energy. However, if the amounts of acetyl-CoA generated in fatty acid ß-oxidation excess the capabilities of the Krebs cycle, due to a lack of glucose and oxaloacetate, it is then used to make ketone bodies which are then used as an essential energy source by the brain and other tissues. KB are converted via several steps to acetyl-CoA, which can be used via the ATP-generating Krebs cycle.
(tl;dr) So, what does all of this actually mean?
First of all, you should know that keto isn’t a new practice. Since 1921, it’s been studied & used as a therapeutic diet in childhood epilepsy. It’s only recently that it’s become popular for use outside of a MD-prescribed, RD-supervised medical setting.
No matter how Jillian Michaels feels about it, there’s a LOT of documented, scientific evidence that the keto diet helps people lose weight quickly (particularly around the middle), improve cholesterol, triglycerides, HDL levels, and blood sugar. And when done properly, it still provides plenty of fiber (20 grams of carbs is equal to about 3 POUNDS of spinach) and it’s low-protein, so it doesn’t increase the strain on the kidneys.
So, yeah, a lot of benefits & many of the risks are exaggerated.
But there’s still a lot of reasons not to eat such a time-consuming & complicated diet.
There are really only a few things we know for-sure-for-sure about nutrition. And the fact that whole grains have outstanding value is virtually undisputed. Not to mention that grains are cheap & fat is expensive (don’t know about you, but I ain’t got money for that). Keto is a lot of work. It requires meticulous tracking all day, every day (don’t know about you, but I ain’t got time for that). While keto is proven massively effective up to 24 weeks, the effectiveness drops over time & equals the effectiveness of more balanced diets over 2 years.In fact, being ketosis has been shown to have no advantage over a more moderate, low-carb diet. Our bodies are designed to run off glucose. Ketosis is working against that design. Case in point: The Alaskan Inuit are the only known population to naturally eat a high-fat, low-protein diet that should result in a constant state of ketosis. However, as their genes evolved with that diet, their genetic code actually began to block that process – proving that our genes do not want us to live in ketosis!
Bottom line: If you’re a hard-charging, Type-A go-getter who loves to go “all-in” then a short-term ketogenic diet is a completely healthy & safe option for you to kick off your weight loss journey. Just set a deadline, and keep your focus on plant-based fats & off animal-based fats.
But if you’re already-busy, already-budgeted, or just more easy-going, then you can rest assured that a slower, more balanced approach is equally effective over time.
Final thought: A large part of what makes all low carb diets so effective is how they balance & regulate the hormone insulin. It sounds complicated, but it’s actually very simple. You can learn all about diet & insulin in my special FREE report, How Insulin Makes You Fat [and What To Do About It].
Do you have any questions or personal experience you’d like to share? Drop a comment!