Saturday, May 16, 2009

Science is Hot: Fat Loss Edition

Science is Hot: Fat Loss Edition

This is the second post is our "Science is Hot" series, featuring Mathieu Lalonde, a chemist with a lifelong interest in nutrition and human performance. As a reminder, Matt obtained his bachelor's degree in science with a concentration in chemistry from the University of Ottawa (Canada), and a PhD in organic chemistry at Harvard University. He is currently pursuing post-doctoral studies in inorganic chemistry at Harvard. (Translation: Matt is scary Smart.) In addition, Matt has a real gift for translating complicated and highly technical concepts into practical, applicable advice tailored specifically for CrossFit athletes.

Our first 
Science is Hot post came from some conversations I had with Matt while hanging out at the Science Exercise Certification in January. Over the course of the next few weeks, that post received more hits than any other entry in the history of this blog. Because of the response, and as a result of the huge number of questions I've been responding to lately about performance, nutrition and fat loss, the second post in this series deals specifically with that subject.


Let’s talk about fat loss. Isn’t it just a matter of “calories in, calories out?” 

“Calories in, calories out” belongs on the shelf of flawed hypotheses, right next to “a calorie is just a calorie”. Gary Taubes does a good job of debunking these myths in his book entitled 'Good Calories Bad Calories'. The "calories in, calories out" hypothesis arises from the application of thermodynamics to the human body. Energy conservation tells you that:

ΔE= Ein – Eout 

ΔE is the change in energy, Ein is the energy intake (typically in units of calories), and Eout is energy expenditure. From this simple equation, it appears that weight loss should occur if energy expenditure exceeds energy intake. In other words, a caloric deficit (i.e. ΔE is negative) must be created in order for weight loss to occur. Wouldn’t it be great if it were that simple?

The problem with “calories in, calories out” is that Ein and Eout are assumed to be independent variables - that you can reduce Ein 
without changing Eout. In reality, the two variables are somewhat dependent. For example, if an individual consumes an amount of calories that is near or below starvation levels, the individual's basal metabolism will decrease in an attempt to conserve energy. In this case, reducing Ein led to compensatory decrease in Eout. (This is why diet and exercise are such a powerful combination; exercise allows one to increase Eout.)

But even then, things aren’t that simple, right? 

Right. Treating the human body like a motor completely ignores all of endocrinology; the hormones involved in the mechanisms of energy storage and release. Therein lies the real flaw of the “calories in, calories out” hypothesis. When endocrinology is ignored, it is easy to think that fat people are fat because they don't exercise or they eat too much. For some folks, that is true. But for people with metabolic syndrome who suffer from chronically elevated insulin levels and insulin resistance, the 
opposite is true. Taubes' genius lies in the fact that he was able to properly identify the cause and the effect. If someone has chronically elevated insulin levels or insulin resistance, fat stores are not accessible for energy. In this case, fat people don't exercise because they are fat, or eat too much because they are fat. Obesity is the cause; lethargy and hunger are the effect. Everything gets turned on its head.

So what about “a calorie is a calorie”? 

"A calorie is a calorie" is simply incorrect because it also ignores endocrinology; in this case the food’s effect on human hormones. 
The source of the calories is just as important, if not more, than the total number of calories itself. A common cause of insulin resistance and elevated levels of insulin in the bloodstream is excess consumption of refined carbohydrates. If individuals with chronic insulin resistance try to lose weight by simply cutting calories or exercising without changing their diet, they will end up losing muscle mass as opposed to fat. On the other hand, if someone with a diet consisting mainly of insulin-spiking foods (sugar, starch, bread, dairy, etc..) switches to a diet consisting mainly of lean meat, vegetables, nuts and seeds, some fruit, little starch, no sugar, no grains, no dairy, no legumes ("Paleo"), then weight loss may occur even if the diets are isocaloric (i.e. have the same amount of calories).

This becomes apparent when high-carbohydrate low-fat diets are compared to isocaloric high-fat low-carbohydrate diets. People on 1,500 calorie high-fat, low carbohydrate diets
lose weight and feel better than people on the same calorie high-carbohydrate, low-fat diets. In fact, cases of severe dementia as the result of 1,500-calorie low-fat high-carbohydrate diets have been documented, while people on a high-fat, low-carbohydrate diet have excellent biomarkers of mental and physical health.

Why is a higher fat diet so important if you’re trying to lose body fat? 

Fat makes it much easier to live on a caloric deficit. The consumption of fat causes the release of various compounds that tell your brain you are no longer hungry.
 Fat consumption also changes the expression of a gene that synthesizes adropin, which plays a role in energy homeostasis and lipid metabolism.

In addition, fat consumption triggers the release of N-acylphosphatidylethanolamine, which inhibits food intake, and foods that are high in fat also have a much lower insulin response when compared to foods high in carbohydrates. This is why Robb Wolf recommends cutting out carb blocks and replacing them with fat blocks for people who are always hungry on the Zone. Not only does subbing fat for carbs prevent hunger, but it also increases the caloric content of the diet.

Fat is also responsible for the synthesis of a variety of hormones. Interestingly, it has been shown that high fat diets have a vitamin sparing effect compared to high carbohydrate diets. Most importantly, as long as fat is available for fuel, the body will not catabolize muscle for energy. 
So the consumption of fat also has a muscle sparing effect.

But we do need SOME carbs.

Yes. Ideally, one would only want to consume enough complex carbohydrates to be able to perform optimally during exercise, with the remainder of the calories consisting of protein and fat. Eating only as many complex carbohydrates as absolutely necessary is especially true if the carbohydrates are coming from insulin spiking sources such as bread. (You shouldn’t have to worry about your intake of vegetables, however.)

So what’s going on with CrossFitters who write to me, saying they CrossFit 3/1 and are only eating 1,400 calories a day… and STILL don’t seem to be losing fat?

There could be a lot going on here. First and foremost, what are these CrossFitters eating? If it’s high carb, low fat, then I’m not surprised. If they are eating Paleo (meat, vegetables, low fruit, with plenty of healthy fats), then the problem might be elevated cortisol levels due to too much stress. 
Stressors include one or a combination of too few calories (i.e. starvation), too much exercise, not enough sleep, as well as a variety of other work or life related factors. 

Assume a CrossFitter is already on a solid Paleo diet. How do they know if they need to eat MORE or LESS to jump-start fat loss? 

It all depends on how much they were eating to begin with – this one is trial and error. If they were eating too much, caloric restriction might see them leaning out and performance could improve. If they were eating the right amount of food and cut more calories, they might get sluggish and become more likely to over train (or under recover). The problem isn’t necessarily one of basal metabolism, which tends to slow down when a significant caloric deficit is created, but rather of energy stores. If food intake is insufficient for replenishment of muscle and liver glycogen, intense bouts of exercise such as CrossFit may become somewhat more challenging. That is because the amount of glycogen used by the body increases with the intensity of the exercise. The glycogen stores of someone on a low calorie diet may not be able to supply sufficient quantities of glucose to maintain a high level of intensity for the duration of the workout. The same can be said of individuals who have to resort to a very low carbohydrate diet (i.e. just meat and vegetables) in order to lose body fat.

Low glycogen stores aside, burning fat for energy (Krebs cycle) requires more oxygen than burning glucose. When oxygen demand is high, such as during most CrossFit workouts, the body will shift energy sources in order to use oxygen as efficiently as possible. If glucose, from glycogen, is not available, fat will be burned for fuel… but less oxygen will be available to the muscle. (As an aside, the purpose of a post workout meal consisting of complex carbohydrates such as sweet potatoes is to replenish spent glycogen stores.)

So if you’re eating to lean out, can you still maintain performance? Or is there always a trade-off? 

It depends on food quantity and quality. If you have a small caloric deficit, your performance might actually improve as you lose body fat. This has been shown time and again by many who follow ‘The Zone Diet’ or ‘Paleo/Zone’. Unfortunately, ‘The Zone Diet’ doesn’t work for everybody. In the case, a ketogenic cyclic-low-carbohydrate diet is typically the way to go. Decreased performance is almost a guarantee here, however, given that the point of the diet is to deplete glycogen stores to allow fat to be burned for fuel. The cyclic nature means that you gorge on complex carbohydrates at specific meals and specific times in order to replenish spent glycogen stores. A male CrossFitter on a Paleo diet with an already low body fat level between 10% and 15% can further decrease his body fat level with a ketogenic cyclic low carb diet, but performances will suffer to some extent. You can find a great description of a CLC diet in Rob Faigin’s 
Natural Hormonal Enhancement.

How do I figure out how much I need to eat to cut body fat without sacrificing muscle?

If you exercise regularly and your protein consumption is adequate for the amount of exercise that you perform, it is unlikely that you will lose a significant amount of muscle mass. The amount of food required will be found through trial and error, sticking with each “phase” for two weeks to one month before evaluating the effectiveness and making changes. Exercising during this whole process is key. Here is what I would recommend.

1. Use the Zone Calculator to determine your protein intake. Have protein at every meal to meet this intake and use lean meat (preferably grass-fed), fish and sea food, poultry and wild game as well as eggs as your main sources of protein.

2. Eliminate highly refined and sugar laden foods from your diet. Replace some of the calories with foods containing good fats like olives, avocados, coconut, nuts and seeds.

3. Eliminate foods made from grains or grain-like substances (such as buckwheat). Breads, cereals and pasta are the number one targets here.

4. Eliminate dairy.

5. Eliminate legumes.

6. Eliminate dried fruit and fruit juice. Try to eat more vegetables than fruit. If you eat fruit, make it fresh fruit.

7. If you are down to lean meat, eggs, fish and seafood, poultry, vegetables and good fats and still not losing body fat, then slowly cut the calories from fat until you start to lose weight.


In summary, food quality ("Paleo") is both the most important factor in your diet - and also where you'll see the most bang for your buck. Fat is your friend. The Black Box is important - get your quality in line, then start playing around with quantity and macronutrient proportions. Change things one at a time, so you'll know what's working and what isn't. And recognize that for most of us, in the quest for fat loss and the perfect six pack, at some point, there ARE performance trade-offs.

Post any follow-up questions to comments. Matt will do his best to answer them, but is leaving on Friday for the Eastern Canadian Qualifiers. If I can, I'll pick up where he left off, or I'll recruit Dallas to help out (since almost everything I know about diet and nutrition, I first learned from him).

Best of luck this weekend, Matt, and thanks for dropping more of your Science-y genius on us.

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