What is the Keto diet?

I've never heard of this diet until I got my vsg surgery.

Is it a lifestyle or a fad diet?

I've seen so many people say they lose a lot of weight and I'm sure I can look more into it, but I'm curious about those with the sleeve and this diet and what it's about. How it works? Does your surgeon encourage it?

Keto is short for ketosis. This is a state when your body doesn't have any carbs to burn for energy, so it turns to burning fat instead. (More info here.) A keto diet is low in carbs and high in fat, and helps your body stay in a state of ketosis.

There's actually quite a bit of scientific evidence showing that it can work well for obese patients, and it may actually have some benefits to the brain as well. (Example here.)

This is actually fairly similar to the "standard" post-op diet for VSG patients, which should be very low in carbs and high in protein. So if you're already following the appropriate WLS eating guidelines, it's not a huge switch to go keto.

Keto is high fat, medium protein, very low carb. I switched from the standard post-op high protein, low fat, low carb diet to Keto at about 5.5 months post surgery. I wouldn't suggest trying it before that because with such small food intake in the first several months, you need to get in your protein, that's most important. For keto to work, you MUST have a minimum of 65% of your daily calorie intake come from fat (75% is better but nearly impossible to achieve unless you are in maintenance). There just aren't enough calories to do that and get your protein in every day.

Once you can bump up your calories and are eating more, then you may want to give it a try. I stick to 60g of protein per day, and then provide the majority of the rest of my calories from healthy fats and a few veggies (usually things like zucchini, cauliflower, broccoli, or leafy green salads).

At my 6-month check in when I told my surgeon I had switched to keto, he was happy with it but would not have approved if I had switched earlier. Just had my 1-year checkup and the surgeon and program were thrilled with my progress. I have lost 83% of my excess weight and met my initial goal at 10.5 months.

Ketogenic diets first appeared in medicine to treat epilepsy, particularly in children, actually. Ketogenic diets restrict total carbohydrate intake to a very low amount, typically 20g or less, in order to achieve a therapeutic effect, typically. They force the body to use fat for the primary energy substrate rather than glucose, and they also cause insulin levels to drop. This tends to 1) cause less inflammation and pain systemically, as insulin is highly inflammatory and 2) make it difficult to store fat, as low levels of insulin make it extremely hard for the body to store fat rather than using it. Insulin is also one of the big culprits in cardiovascular diseases. If there's a pothole in the road, it's not your tire that damages your car, right? Fat gets caught in the arteries damaged by carb overconsumption and higher insulin - it's not that fat that causes the damage. However, this is a tangent.

I follow a modified version to get 90g of protein a day, however I have a well-educated surgical team and they have always supported my diet. Many people are in ketosis eating far more carbs too, FWIW...it's just that 20g guarantees it.

Ketones bodies are made in the liver by breaking down fat. The liver is like, a powerhouse of metabolism. The majority of individuals who adapt to being on a ketogenic diet tend to do far better biologically. There is a period of a few weeks (sometimes longer) where people feel unwell due to the body shifting around processes, however after fat adaptation things stabilize considerably. A few rare metabolic disorders are contraindicated...porphyria comes to mind, as individuals with this disease often have issues with certain liver pathways needed for ketosis.

You have already been in ketosis if you have ever breastfed, lost weight, or slept. The body does not need glucose for energy for the most part. For example, the brain prefers ketones as the article which Julie posted mentioned. A dude named Cahill wrote a study called "Starvation in Man" and he determined that the majority of the brain's energy shifts from being glucose dependent to ketone-body dependent. He determined this with jugular catheters which...makes me really glad I did not do clinical trials in the 70s! Anyway...

Only the medulla area of the kidney, some bone marrow cells, and some other cells too small for other processes to be performed (some glial cells) cannot use ketone bodies. This is why we can make our own glucose, to support these processes. Part of why it's so vital for DS patients to get protein after surgery, for instance, is that if our protein levels drop significantly, the body begins to catabolize its own structures to break down protein and supply the body with both glucose and building blocks for repair. A lack of protein or fat will kill you, but a lack of exogenous (external) carbohydrate is inconvenient biochemically.
Ketosis is a metabolic state that occurs when your body cannot utilize glucose as the primary energy source. The body then undergoes several metabolic changes to burn fat instead, and to use this as the fuel for cellular energy versus glucose.

We actually use three macronutrients we can utilize to function and repair our body's cells. (We actually need a whole lot of other stuff besides macronutrients, but let's stay simple for now.)

These are: carbohydrates, protein, and fat. Fat is broken down into lipids, proteins are broken down into amino acids, and carbohydrate is broken down into glucose. In order to absorb food, it has to be in the correct forms, and so the digestive tract processes these, dismantles them into far more basic components, and then shunts them off in the body where they are needed. We cannot make fat or protein, so we must always consume those in order to survive. We can, however, make glucose in the liver via a process known as gluconeogenesis. Additionally, we can store all of these when there is a surplus to varying degrees. This is determined by energy balance to some degree, however it is also heavily influenced by hormones, insulin being a key one. Hormones drive fat storage and not overconsumption of food. Overconsumption of food alters the hormones which can result in more energy being stored than should be. I'd actually argue obesity and overeating is just a symptom of a different issue, usually behavioral and (more rarely) something genetic like Praeder-Willi...but I digress.

So, it's not really just calories that cause what gain - it's what we eat too. Obviously both ideas have their rational limits; there must be a balance in consumption in terms of volume as well as food type. Both are equally important.

What's most important is keeping serum insulin level consistently low. Even if you don't eat a ketogenic diet, eating a lower carb diet will do this. The 100g/less a day that nutritionists espouse for bariatrics is a good start if you don't want to do a ketogenic diet, too. As an experiment, I tried to do that last year for a week, eating protein first and then carbs. Literally after eating meat I can't eat more than maaaaybe 1-2 tsp of rice. I wound up at 40g/carbs a day tops, just because Harvey wa****ting max capacity measurement wise (yes...I still measure over two years out).