I lift heavy weights 3x a week on low carb with no problems. In addition, I also did couch to 5k 2x a week for the last year. The whole point of low carb is that the fat IS the fuel source, instead of carbs. The good thing about Science is that it's true whether or not you buy it

But seriously, I tried EVERYTHING else first. EVERY. THING. I gained weight last year despite reasonable calorie restriction and exercise.This was before I was diagnosed with PCOS. I reduced carbs, kept my protein and calories exactly the same, and I've lost 31 more pounds since Jan. A lot of people with healthy metabolisms and endocrine systems can lose weight on calorie reduction alone. People who are not so fortunate, especially with insulin resistance, cannot.

I lost 42 lbs on my own with a 'normal' lower calorie diet. Then I hit a wall. I fought that wall for almost 2 years before I got treatment for my hormonal issues and changed my diet. For me, the old saying is true: "lifting weights doesn't make me bulky, eating cupcakes does." I agree that you should eat as many carbs as you can and still lose weight. I have to keep my net around 50. 150g/day I gain. I eat one big high carb meal a week for my glycogen, but my lifts and workouts have not suffered after the first month of carb flu.

If this science is "true" (which i don't buy because I believe that there is no one diet out there for everyone. There is also scientific "evidence" promoting just about any diet out there. It's all marketing) why was I my lowest weight when my staple was whole grains, veggies, and fruits? I beat insulin resistance with this diet. I don't really buy into the idea about one specific macro being bad. I think it's all about quantity and the quality of food (eat nutritious food) This philosophy, along with regular exercise, has kept me at a healthy bmi for 10 years. Again, this is what has worked for ME

I think her mentioning of science was in response to the line

but I definitely eat CARBS because they fuel my body

On that front, the science is clear and in no way controversial -- when you reduce your carbs to the point that the body cannot rely on it as a primary source of fuel, it looks to fat for that fuel. This happens with every body. If it didn't, you wouldn't ever be able to lose weight, because your excess weight is composed of fat.

She even said that she agrees that you should eat as many carbs as you can that won't stop you from losing weight. If it's 150g, great! If it's 50g, that's fine, too.

I don't think anyone here has said that "one specific macro is bad." Everyone has said that many women with PCOS with insulin resistance do better on a low-carb/high-fat diet, because we don't generally process carbs that well. If you've found that you do well on a higher-carb diet, then great! That doesn't mean LCHF is something to "buy into," it just means you don't have to do it to manage your weight, if you don't want to.

I've never bought into it either in a lot of ways. The body and especially the brain needs carbs.

The body doesn't need carbs/glucose at all to function, everything except the brain can run on ketones or free fatty acids directly. The brain does need some glucose, but the body can make most of what it needs, even in the total absence of dietary carbs.

There is actually growing evidence that the brain works best on a combination of ketones and glucose, and this set of evidence has been growing for the past century, ever since the ketogenic diet was first introduced to help epileptic patients.

It basically works like this -- ketones are actually a more stable source of fuel than glucose. The body prioritizes glucose over nearly everything else, not because it's a "preferred" fuel (if it was really preferred, the body would store more than about 100g of it in the body), but because glucose is toxic in blood concentrations higher than 140mg/dL post-meal, or over 100mg/dL sustained/fasting. At these levels, it starts causing organ, nerve, and other damage to the body. Because of this, the body goes to great lengths to keep that number down (insulin has been so important that even the most basic of animals produce it). Unfortunately, the myth that you have to eat a bunch of carbs persists. The body can make the bulk of the brain's glucose needs through a process called "gluconeogenesis" (literally, glucose creation), in which it takes fat and amino acids (proteins) and creates glucose from it. This, combined with ketones, can provide the brain all the energy it needs.

Ketones are a glucose-like source of fuel that the rest of the body, and parts of the brain can use instead of glucose. It's what the body uses any time you go more than about 6 hours without eating, such as when you're sleeping, as they're a by-product of burning fat. These ketones have been shown to reduce seizures, migraines, symptoms of Alzheimer's and Parkinson's, and numerous other issues.

The common denominator in nearly everything that both the benefits of ketosis and problems of hyperglycemia?

The brain and nervous system.

If the brain and body actually needed upwards of 50% of our energy intake to come from carbohydrates, then why do the very things people say absolutely must have from diet, actually improve when that thing is all but removed? Because the body has ways of meeting the brain's needs. It's part of what has gotten us to where we are, to begin with.

The fun part is, though, is that it's not an all-or-nothing thing. You don't have to choose between 20g of carbs and 200g. You can still see benefits of lower carb eating even around 100g. It depends largely on what your needs (including non-dietary) and goals are.

Here's some info regarding the myths and facts of how the body and brain uses glucose, what happens when blood sugar is too high, and the studied benefits of ketogenic diets:
http://www.diabetesselfmanagement.com/Blog/David-Spero/glucose-how-high-is-too-high/
http://www.phlaunt.com/diabetes/14045678.php
http://diabetesupdate.blogspot.com/2008/11/myth-busting-your-brain-and-that.html
http://blogs.scientificamerican.com/mind-guest-blog/2013/10/01/the-fat-fueled-brain-unnatural-or-advantageous/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2367001/
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3321471/
http://www.psychologytoday.com/blog/evolutionary-psychiatry/201104/your-brain-ketones
http://www.nerdfitness.com/blog/2013/06/17/everything-you-need-to-know-about-sugar/
http://www.webmd.com/diabetes/how-sugar-affects-diabetes?page=2

I was watching some videos on the book The Calorie Myth and want to check it out but also in that book I take it, it describes low(er) carb eating too. But some of the things he mentioned in video he did for Microsoft research talks was just thought provoking. Once was about how the body keeps burning what its used to and for many that becomes sugar with carbs and sugar consumption. To burn fat he basically mentions getting the body to switch from wanting sugar to fat. That way when fat from consumed foods run out its goes for the fat stores. Sugar is different because we don't store sugar as sugar or something like that. I sure hope the book explains things or I can find research on it.

The author says that it's not a "low-carb" diet. In fact, he insists on at least 10 servings of non-starchy vegetables a day. It is, however, probably lower carb than what people who have been following the Standard American/Western diet are probably used to. With the amount of non-starchy vegetables that he recommends, you're probably looking at around 100-150g of carbohydrates, total.

His stance is "protein, fiber, water" as the key to maintaining health and a healthy weight, without feeling deprived. If you ensure you're getting plenty of nutrients (though lots of vegetables and good proteins), then your body will handle the weight part on its own.

I don't recall him saying anything in the book about the body burning what it's used to. In fact, he doesn't encourage much in the way of fat. His general stance of fat consumption is from "whole-food sources" -- so your fat intake should only come from the fat in the meat, coconut, nuts, or avocado (etc) that you're eating, and not from added fats/oils (even avocado or coconut oil). Personally, I found this stance a little double-standarded, as he encourages the use of protein powders and smoothies to get all your protein and vegetable servings in. If he supported the idea that "you burn what you're used to," the diet in The Calorie Myth would encourage the burning of protein, not fat.

We don't store sugar as sugar, for the most part. About 100g gets stored as glycogen (depending on demand, people who use it more can store a little more). The rest gets sent to the liver and turned into triglycerides. This is largely why people with metabolic disorder, insulin resistance, etc, are also at higher risk for cardiovascular issues. Eating a diet higher in carbohydrates than their body can handle results in elevated triglycerides and lower HDL. Even in healthy individuals going from SAD to a high-carb whole-foods based diet, triglycerides don't change, and why going to a high-fat/low-carb diet consistently produces the most marked reduction in triglycerides.

http://authoritynutrition.com/23-studies-on-low-carb-and-low-fat-diets/
http://www.ncbi.nlm.nih.gov/pubmed/9805219

I have lost over 100 lbs with insulin resistant PCOS also on 2000 mg of Metformin. I follow a similiar diet just minus the refined carbohydrates. I do just fine with it.

I have really gone back and forth in terms of reducing carbs. I really love them and don't want to give them up, so if I can lose weight and eat them I'm a happy camper. That being said, it is definitely very easy for me to gain the weight back (which is what happened this past year with crazy life changes and not sticking to my workouts as I used to do) when I don't watch the carb intake. As I start this process over I'm going to try to hit my calorie goals first and be conscious of carbs without specifically counting them. If I don't see results I will reduce carbs and see if that's the trick.