This might seem obvious to a lot of people now — but 20 years ago this concept was revolutionary: Carbs… not fat… cause people to store fat. There are a zillion websites and medical journals that explain this better than I can, but here’s the basic breakdown:
Calories are how we measure food-energy provided to your body. You can get energy from anything with calories (basically, any food). That energy comes from carbs, fat, and/or protein. But each of these sources plays a very different role. In order to understand why and how carbs can make you fat, you need to understand the pros and cons of getting your energy from carbs vs. fat vs. protein:
The difference between Carbs / Fat / Protein:
Carbohydrates are a highly-efficient source of fuel (because your body requires less oxygen to burn carbs compared to protein or fat). During high-intensity exercise, when your body can’t process enough oxygen to meet its needs, carbs are the go-to energy source!
Fat is a highly-concentrated slow-burn fuel. It has more than twice the energy per-gram as carbs or protein, and it’s the preferred fuel source for moderate-intensity exercise and “at rest” activity. (In many cases, fat will contribute 50%, or more, of the energy your body needs for day-to-day activities). Fat is also the ideal energy source for long-duration workouts.
The normal role of protein is to help repair and build muscle and other tissue in your body. Protein is a very low-quality energy source, but can be used in an “emergency” if your body isn’t getting enough energy from carbs or fat. In a situation where you’re not feeding your body enough carbs or fat to produce the energy it needs, your body will either use the protein in your diet, or start burning its own muscle, to get a low-quality energy source. (Side note: This is why you can’t safely lose more than about 2lbs per week. Your body isn’t capable of burning fat any faster than that — and if you ARE losing weight at more than 2lbs per week, those pounds are coming from muscle, not fat!!)
To summarize all of this.. Carbs are the most efficient fuel source, providing shorter, stronger bursts of energy. Fat is your “slow burn” energy. The day-to-day stuff needed to run normal functions. And we want to avoid using protein as an energy source at all.
Impact of fat vs. carbs on blood sugar
Energy to your body can be measured by checking the glucose levels in your blood. (Diabetics do this all the time, and if you’re serious about learning how foods affect your body, you might consider buying a glucose meter yourself!)
Fat in your diet will produce a slow, steady, level of blood-sugar. This is great for normal, day-to-day activities. It’s the ideal energy-source for sedentary activities. Carbs, on the other hand, will provide a short-term “spike” in blood-sugar to fuel a need for quick energy. Thing of it like a turbo-charger. They’re great for fueling high-intensity exercise! (If you’re breathing heavy, carbs are the fuel you want!)
Not all carbs are created equal
Some carbs will cause a MASSIVE spike in your blood sugar, and some will only cause a minor spike. It really depends on how “complex” the carbs are.
“Simple carbs” (like sugar, white-wheat, etc.) are so dead-nuts simple for your body to process, the entire result of those calories is converted straight to blood sugar energy. More “complex carbs” (like whole-grains) require a lot of extra work for your body to process and result in a much more sustained and controlled blood-sugar increase.
Simple carbs cause instant, massive spikes in energy (think “sugar rush”) that usually result in an energy crash, causing your body to crave more of the same. Complex carbs (“clean carbs”, as most people call them) provide a longer-term, sustained release of energy.
In other words, simple carbs bad. Clean carbs good.
Examples of Complex Carbs (“Clean Carbs”): Beans, whole-wheat, oatmeal, brown rice, carrots, barley, and bran.
Examples of Simple Carbs (“Dirty Carbs”): Apples, oranges, bananas, sugar, white-bread, and white-rice.
The Glycemic Index
Fortunately, there’s a simple way to tell whether a carb is clean or dirty… Introducing….. the glycemic index! One of many new tools in your weight-loss arsenal. More information here… but essentially, the higher the food is on the index, the more likely it is that eating that food is going to send you in the wrong direction. http://www.glycemicindex.com/ — foods below 55 are considered “low”.
So what happens if you eat dirty carbs that spike your blood-sugar levels?
Well, it’s not necessarily a bad thing (if you need the energy) — in fact many marathon runners will eat huge quantities of sugar during their races. I eat a banana before every run because I WANT that short-term energy burst and I put it to good use. But most of us spend all day every day sitting around. We eat a carb-heavy meal (like pasta, or pizza, or a sandwich with white-bread), and then we sit back down at our desk and go back to work. (So unless you’re an athlete, or you spend a fair amount of time at the gym, simple carbs have NO place in your life).
Why Dirty Carbs Make You Fat – FAST
When your body has excess energy that is has no need for… (e.g. you eat the simple carbs, your body produces blood-sugar, but you don’t do anything active after you’re done), any food sitting in your stomach will get converted to fat. (Because your body says “Well, we’ve got all this fuel, so no need for this extra food.. STORE IT FOR LATER”).. and thus, you add weight. I’m oversimplifying, obviously, but this is an easy way to visualize it.
Put another way, if you eat simple carbs but don’t use the short-term bursts of energy that result, your body will use that energy to store the food sitting in your stomach as fat.
So you can see why foods like donuts or pizza are the perfect-storm for weight-gain.. Donuts are LOADED with carbs AND fat. So you eat the donut, which produces a blood-sugar spike, but then sit on the couch and watch TV. Your body responds by taking all the fat from the donut and storing it for later. So even though that donut was only 400 calories, almost 100% of it goes straight to your hips. (Same for pizza!)
This is also where a lot of people screw up from the very beginning.. You know how we’ve always been told that “eating lots of fruits and vegetables is the key to weight loss” ? Yeah. Guess which foods are VERY VERY high on the glycemic index? Most fruits and many vegetables. Eating pineapple, oranges, and potatoes is an instant recipe for weight-loss failure.
This is yet another proof point that not all calories are created equal. If your calories come from sugar, along with fat at the same time (the “donut” example), you’re far more likely to store those calories as fat, versus if those calories had been from different sources at different times of the day.
Simply put, I would avoid any and all foods that are high on the glycemic index, unless you’re intentionally using them as a short-term energy source before or during a workout. This means no more white-bread, avoiding most fruits, no fruit-juice, and I hope it goes without saying, but any and all sugar.
Note that IIFYM says you can eat whatever you want as long as it fits. However, IIFYM doesn’t distinguish between low-glycemic carbs and high-glycemic carbs. It’s your job to make smart choices in this respect.
Do you even need carbs?
If you’re trying to lose weight with minimal exercising, I would consider cutting the carbs to an absolute minimum (you don’t need them, and fat is a much more efficient energy source for sedentary activity). Adjust your IIFYM ratios for a low-carb / ketogenic approach to dieting (perhaps 15% carbs, 20% protein, and 65% fat).
Cheating is disastrous when it comes to carbs
One warning… simple carbs create cravings for themselves. Your first 3-4 days of eating this way and you’re going to CRAVE simple carbs and sugar. You’ll CRAVE bread. You’ll CRAVE your favorite sugary snacks… but I promise if you STICK TO IT and don’t give in (AND DONT CHEAT!! NOT EVEN A LITTLE BIT!!), after a few days those cravings will go away and you won’t miss them. You may also find that your body reacts negatively to not being fed simple carbs. You may even have flu-like symptoms for a few days and think that’s a sign your body isn’t getting the calories it needs. Total crap. Keep at it. Your body is detoxing. It doesn’t last long.
People constantly dealing with cravings, or constant demands for sweets are typically cheating every so often. Those cheats are catastrophic. They ignite cravings. Be strong. It might only be 50 calories, but the blood-sugar spike that results will reignite cravings. It’s not worth it.