Need to lose fat? Eat less food.
Physicists love this answer and usually expect the story to end there. Take a trip to any bookstore in the country and check out out the collection of "diet" books and you'll see that it's not quite so simple.
Let's start with some caveats and good news: The fatter you are, the worse your current diet, and the more out of shape you are, the better your results are going to be. A 400 lb. couch potato who eats 12 Big Macs a day will have a much easier time losing 10 lbs. than a fit chronic dieter with a small spare tire obscuring his abs. What that means is that the things that will work for that 400 lb. hypothetical person may not work for their more fit counterpart. The fitter you are, the closer to an ideal weight (which means your abs are clearly visible and nothing jiggles when you move), the harder it's going to be to make those final few improvements.
So if you're really, really fat, just eat less and start doing some light exercise and watch the pounds melt away. Until they stop (which will happen eventually).
When the simple measures have stopped we have to start putting more thought into what we're doing. Let's start by thinking about our goals: We want to lose fat. We want to lose it quickly. We want to do so in a psychologically sound way (if our diet makes us feel hungry and miserable all the time we won't stick to it). We want to maintain or improve our health while we do it. We want the fat loss to be sustainable. We want to minimize or avoid entirely the loss of muscle mass while we lose the fat.
How do we manage all those things at the same time? Most diet plans fail on one or more of these goals. Low fat diets tend to fail miserably on both the health and psychology axes - they make us miserable and eating low fat just isn't good for you (despite the conventional wisdom). Starvation diets aren't comfortable or sustainable. Fasts like the juice fast sacrifice lots of muscle and are not sustainable or healthy. You see where I'm going with this.
You have to address two opposing goals: you need to eat enough food to get the nutrients you need to support your training, your health, and your mood, while eating a small enough amount to create an energy deficit and make your body burn fat. The keys to doing this is to eat nutrient dense food - that is, food that has a lot of good nutrients for a given amount of calories - while avoiding food that is either empty (has calories but few or no good nutrients) or, worse, full of antinutrients (substances that actually damage your health or ability to lose fat, like gluten, lectins, trans fatty acids, and high levels of fructose).
Let me break this down a little bit.
Get rid of all the empty calories in your diet. A classic example of empty calories is soda - water, high fructose corn syrup, and flavorings. There's basically nothing good for you in it (I'm assuming here you have access to a normal variety of foods - drinking soda is better than dying of dehydration, but that's not the choice facing most of us). Highly processed foods fall into this category - most of the stuff from the inner aisles of a supermarket.
Get rid of foods high in antinutrients. Immediately stop eating any foods that contain artificial trans fatty acids - anything with "hydrogenated oil" on the ingredient label. Reduce greatly your intake of simple sugar. Stop eating any foods containing or made from wheat or legumes (beans). You should probably limit or eliminate all dairy other than cream and clarified butter. Reduce your intake of fructose as much as possible - you can eat some fruit, but don't go crazy on it, and eat no high fructose corn syrup. Artificial sweeteners are a somewhat controversial topic, but you should probably avoid or eliminate them as well (this is a case of do what I say, not what I do, but I'm trying to overcome my diet soda addiction, I promise!)
If you want to know why I'm making these specific recommendations it's a long story. Fructose induces hepatic insulin resistance, and if you're having trouble losing weight there's a good chance you have insulin problems. Wheat and legumes cause immune responses that lead to greater insulin resistance and inflammation. We did not evolve to eat those foods and can't tolerate them. Sorry - I understand that many of your favorite foods are made from wheat, so are mine, they still aren't good for you (I'll delve into this issue more specifically in another post one day). Artifical sweeteners induce an insulin spike, and insulin is pro-inflammatory and may contribute to insulin resistance, as well as promoting fat storage and preventing fat breakdown.
If we shouldn't eat all that, what should we eat?
Start by making sure you eat enough protein. You need roughly .75 grams protein per pound of lean bodyweight per day, give or take. If you're 200 lbs. with 20% bodyfat your lean body weight is 160, so you should shoot for at least 120 g protein per day. Going higher is okay healthwise, but there are some reasons to not go too high. If you eat a lot of excess protein your body will use it for energy, which is okay, but then your body gets used to using protein for energy, and if you run into a period of time where your protein levels decrease (vacation, whatever) you might start impacting muscle mass as your body dips into protein stores to supply energy. Not a huge problem, but consider it. You also can't eat a predominantly protein diet - there's an upper limit past which you'll die. Look up "rabbit starvation" for more details.
I get my protein by making sure to eat a pound of beef a day. Choose your own method.
You need a nice chunk of omega 3 fatty acids - but not just any omega 3 fats. Your body can only use some of them in real quantities - focus on getting EHA and DHA. Sorry vegans, you can only get the good omega 3 fats from animals or fish - the omega 3's in flax or other plants aren't usable by humans (we can convert small amounts of the short chain omega 3's into usable forms, but only a small percentage, and the rest goes to bad places). Fish oil is good, as is grass fed and grass finished beef and wild caught fish. If you're vegan, then... stop being vegan. At least if you want to maximize your health.
You should get the bulk of your calories from a nice mixture of healthy fats. Saturated fat is good (no, it won't clog your arteries or give you diabetes, that's a myth). Monounsaturated fat is good. Think nicely marbled grass fed beef (grain fed beef has too little omega 3 fats and too much omega 6 fats). Limit your omega 6 fat intake as much as you can - you probably get waaay too much of it in your diet. That means no modern oils - no canola, vegetable oils, corn oil, safflower oil, etc. Olive oil is okay (mostly monounsaturated), coconut oil and red palm oil are better. Lard and butter (from grass fed animals) is even better. Be careful heating olive oil, though, it will go rancid very quickly under heat, which you would know if you paid attention in high school chemistry. This also means you have to restrict your nut consumption - almonds are great, but they're high in omega 6 fats, and eating a lot of them will lead to inflammation problems.
What about carbs? I used to be a strong advocate of a very low carb diet, but I'm changing my tune slightly. If your primary concern is health and longevity and your training is moderate you can get away with a zero or close to zero carb intake and probably be better off for it. I find that if I train intensely (which I sort of have to as a karateka) that my performance is limited if my carb intake is too low. Basically, high intensity exercise depends on muscle glycogen for fuel, which has to either come from dietary carbs or protein (via gluconeogenesis). You can either eat some carbs, eat extra protein, or just suffer from flat workouts. I personally prefer to eat some carbs. If you want, do a simple experiment - work out on a very low carb diet, then eat a pound of sweet potatoes, and work out again, and see how it feels. Some people tolerate lower carbs better than others.
Where can the carbs come from if you can't eat wheat or beans? I stick to root vegetables - sweet potatoes, yams, that sort of thing. Is it boring? Yes. Is it worth giving up pizza to have a six pack and be a better fighter? That's up to you. Rice and corn are on the bubble - probably not great for you, but better than wheat or beans. Experiment and see how they affect you.
If this sounds like I'm recommending a paleo diet, that's because I am. I'll explain why more in some future posts, but I'm justifying individual elements of the diet on current research, so even if you have issues with the overall theory I think you'll understand where the pieces come from.
Once your macronutrients are taken care of try to eat some green leafy vegetables for other good nutrients. Lots of other things might be good for you - seaweed, many spices, veggies, some fruits and berries eaten in moderation, black coffee, dark chocolate (85% chocolate has sugar in it, but not a huge amount, so it's okay taken in small amounts if you're capable of that). Some "cheat" nutrients are better than others - that is, eating a small amount of sugar is probably less damaging than a small amount of trans fats, but those distinctions are hard to clarify or justify. Try to eat as "cleanly" as you can.
This is controversial, but I'd also recommend eating less frequently. People all talk about how eating five small meals a day is supposed to stimulate your metabolism, but I don't buy it. I'll write a post on intermittent fasting one day, but I eat all my food in one big meal at night, and other people do well skipping meals or going entire days without food (say, 1-3 days a week without food). The more often you eat the more often you'll be stimulating insulin production, which tells your body to store fat.
Very few people eat this way and stay fat. Stick to fatty grass fed meat (or lean storebought meat), cook it in coconut oil, add some sweet potatoes and a few greens, and watch the pounds melt away. The high nutritional density will keep you healthy. The fat and protein will satisfy you so you aren't hungry all the time. If you need help (like recipes), go through some of the paleo blogs out there - there are a ton of them, with lots of good recipes and articles. I'll post recipes here if I feel the need, but this won't be a good primary source for you (I'm an awful cook).
You may not need to eat this way to get lean. If you're lean already, great. If you drop sugar out and lean out to your satisfaction, great. But if you're having trouble leaning out and sticking to your diet, give this a try for a month and see how it works out.
Feel free to shoot questions my way.