^^^ great explanation!

One of the things to understand is what insulin does. Most people think of insulin as the hormone in your body that enables your body to regulate blood sugar. That is sort of true, but there is another, very important, way to understand insulin. When you put carbs (ie sugars) in your body, your body produces insulin. The reason it does this is to STORE the fat you are putting in your body. Insulin enables fat storage.

So, what happens is that your body is flooded with carbs, so it produces lots of insulin (ie an insulin spike) in order to store as much fat as possible and use the carbs for energy. Until very recently in human history, roughly 1850, the typical human had access to very little dietary sugar, especially fructose, on a daily basis. So our bodies evolved to use whatever energy source that was available, whether it was fat or carbs. Since fat can be stored, but sugar can't, our body also evolved to prefer storing fat for times when it would not have access to energy sources. In other words, when you aren't able to eat every 3 hours.

So, what happens if you eat carbs, get an insulin spike and store all the fat? In a couple hours your body has burned up the glucose, the drop in blood sugar signals your brain that it's hungry and your brain (plus some other hormones like ghreelin) make your stomach growl. If you were to wait and not eat, your body would begin extracting fat to provide energy. However, carbs are readily accessible and you are hungry, so you eat a sandwich. And voila, more sugar, more insulin, more storing of fat. This vicious cycle goes on and on when you are eating 50-60 percent carbs in your diet as USDA recommends.

Your body won't be able to use fat for energy as long as your insulin is high, because insulin tells your body to store fat and burn glucose.

This is the reason why the USDA says avoid fat. The problem is, of course, that fat is what creates satiety in food. Meaning that food tastes good because of the fat in it. If you cut fat out of food, it tastes horrible. Unless you add sugar. Notice that "light" salad dressings are low in fat, but high in sugar. So, what happens when you eliminate fat, but add sugar? Insulin spikes. High blood sugar. Fatty liver. Strain on your heart. Increasing BP. etc.

But does the amount of carbs you eat also depend on the amount of insulin released and fat stored? E.g. You eat a healthy fatty omelette for breakfast, high in fat and protein, basically no carb. Then you have a 100 calorie chocolate bar 10 minutes later. Your insulin would spike from the sugar. Will your body then use the fat from the omelette to store as fat? What is the effect on fat storage and energy use of food if something sweet is eaten with a high fat/protein meal vs just the high fat/protein meal on it's own.

will the fat I'm eating get used as opposed to being stored, as well as my stored fat?

Fat can be stored as fat. Carbs (glucose) can be stored as fat. Protein can be stored as fat (a bit harder chemical process though).
Be careful to not think of dietary fat as adipose tissue (what people call body fat).
If you eat less carbs, but also eat less fat - you will go insane
You will not absorb nutrition.

We americans are the most overfed - but are terribly undernourished because we eat crap devoid of most nutritional content - but also damage the pathways for absorption of what nutrients we do get. example: Taking a multivitamin when your body isn't set up for success is pissing away your money btw

Now that we have you not afraid of fat - start thinking about good fat. olive oil, avocados, grass fed butter and lard etc. Then eat some cholesterol too

Agreed, all macro nutrients CAN be stored as fat. However, the body doesn't really like to store protein and carbs that way. It takes an awful lot of either (and some difficult processes) to do so.

More importantly, your body cannot put fat in your fat cells without insulin. Insulin is the little guy pulling the levers in your body. Insulin tells your fat cells to store fat. Lower the amount of insulin your body is releasing and you lower the amount of fat you store. Take away carbs and your body will have to convert fat in to ketones to provide energy to your muscles and brain. From a science perspective, fat converts to energy much less efficiently than carbs do. It's not like 1g of fat gives you the same energy as 1g of carbs.

That means, from a weight loss perspective, that lowering your carb intake and replacing it with fat intake is going to be good for losing weight. Your body will need to consume body fat to make up the difference in energy levels.

Also, focus on so-called good fats, as noted. Your body processes them much easier. Avoid, obviously, trans-fats. Good fats = EVOO, Coconut oil, grass fed butter and cream, avocados, many sorts of nuts (pistachios - #nom), the fat in grass fed beef, the fat in salmon (and many other fish). I have a cup of coffee with 2 tbsp of coconut oil, 2 tbsp of butter, 1 tbsp of unsweetened cocoa for breakfast .... 97% fat .... I have lost weight, BP has gone down to healthy levels, cholesterol is now in the healthy range. My doctor hates my diet, but can't argue with my health. :-D

Shannon, it definitely requires a change of mindset. Fat has been vilified for so long with no distinction between the different types. Reminds me of the China study and red meat.

It took me a lot of reading and research before I was convinced. And several years of trying doctor and USDA recommended diets and exercise plans that always failed. I got fatter, my health indicators (BP, resting heart rate, cholesterol, blood sugar) got worse and worse too. I reached the point where I intellectually believed the research but couldn't get myself to do it because it went against everything I'd been taught basically my whole life.

Finally, I decided I would just try it for 6 months. Started with Gary Taubes recommendations, moved to Mark Sisson after that. I just gritted my teeth and did every day. And within a few months I had lost a bunch of weight, was able to run 2 miles in a reasonable time and felt great. But it wasn't until I had my annual exam that I really believed it deep down. When my cholesterol had gone from 280 to under 200, my BP from 140/90 to 110/70, my resting heart rate from 80 to 58, my fasting blood sugar from 135 to 97 and I had gone from 218 to 193 in weight.

My doctor truly hates my diet. She argues against it every time I see her. But she then turns around and says that I'm one of her very few metabolic syndrome patients who has actually gone from unhealthy to healthy, so keep up whatever I'm doing.

Because my doctor follows the USDA recommendations. She believes that this is happening because of my exercise, not my diet.

My doctor just told me to keep doing what I'm doing and how glad he is to see his 'healthy' patients once in a while.

I also highly recommend reading Gary Taubes book "Why We Get Fat: And What to Do About it." I just finished it (in two days) and it explains in great detail the role that insulin plays in fat storage. It's very informative, eye-opening, and it will piss you off because of all the misinformation we've been fed over the years about fat. A very powerful book.

Does this mean that if I eat fat with fruit, the fat will be much more likely to be stored as adipose tissue than used as fuel? Is the best think I can do to avoid scoring energy as fat is to not eat sweet or sugary foods with fatty foods? I've been eating sweet potatoes with fatty fish like sardines, then I'll have an egg and an apple. Is this a bad combination?

Heh, I am having a hard time answering just cause I don't like sweet potatoes or sardines. ;-)

I think the answer is that if you are moderate with such foods, and sticking to the right quantities and types of foods, you are not going to see the dietary fat be stored in your fat cells. There's a dramatically different impact on your body from 1 cup of strawberries and 1 cup of pasta. For example:

1 cup spaghetti - 220 cals, 42.8g carbs, 2.5g fiber

1 cup strawberry halves - 49 cals, 11.7g carbs, 3g fiber

We are really talking about the insulin spikes caused by processed foods made from wheat and corn and other starchy foods. Like pasta, bread, anything with HFCS in it, regular potatoes, rice, etc.

Thanks, I really appreciate your answer.
I have a feeling I am very sensitive to certain whole foods, even in smallish amounts. One of my CrossFit trainers recently told me I should be eating more carbs and less fat to furl my body for intense workouts - I was eating equal amounts of fat and protein, approx 100g and 60g carbs. I stopped cooking with evoo and ghee, cut nuts and ate more berries and carrots. The result was exhaustion, napping, weakness and general lethergy. So I think I sugar crash even with "low GI" whole foods and subsequently my body becomes a fat storing machine, from eating a couple servings of carrots and berries! I don't think there is a one size fits all approach with macros or types of carbs. I'm still trying to find a food routine that works.