Monthly Archive: July 2012

Do you have to eat every 3-4 hours to increase your metabolism?

This broke my heart, because I am the Queen of eating every few hours. Initially I was really only hungry 3 times a day, but in every magazine I read it said to eat small meals every 3-4 hours. Now I need to eat every few hours or else I feel like I’m starving. But enough about me, let’s talk about how false this is.

This study is my favorite. They took a few obese women and put them on a 1,000 calorie a day diet. Some of the women ate the 1,000 calories in two 500 calorie meals, the other group ate the 1,000 calories split up over the day. What did they find? At the end of 4 weeks the weight loss was the same in the two groups – they lost about the same amount of fat, muscle, etc. They found that the energy expenditure and the diet-induced thermogenesis (what people THINK is an increase in metabolism when you eat multiple times a day) were the same in the two groups. The most interesting part of the study, however, was that after 4 weeks the “nibbling” group had a decrease in sleeping metabolic rate. So the group that ate twice a day had a higher metabolism at night while asleep than the nibbling/grazing group. This study found the exact same thing.

This study takes it a bit further. They looked at it from a weight loss and satiety perspective. Shouldn’t the people who ate multiple times a day be less hungry, and therefore have less Ghrelin, the hormone that stimulates appetite? PYY, the other hormone, does the opposite – it tells you your full. Shouldn’t people who “graze” or “nibble” have more PYY and less Ghrelin during the day? Nope. Both people who ate 3 meals a day and those who ate 3 meals + 3 snacks had the same levels of both hormones. Well, there goes that.

Kinda on the same vein another study looked at how eating 2 meals a day and eating 3 meals a day affected weight loss. Eating 3 meals a day showed an increase in 24h fat oxidation over the 2 meals, but had a lower fat oxidation at breakfast (fat oxidation = breaking down fats in the body into smaller pieces to use for energy). Not surprisingly they found that the people reported feeling more satiated over 24hours with 3 meals a day than 2. However, this differed from the previous study which measured levels of the hormones responsible for these feelings. In this study, they asked the subjects, meaning this finding may be just based on people being used to eating multiple times a day, or the thought of not eating, etc. If you read the conclusion of the study they get all sciencey and brainy on it, I’ll let you make your own decisions.

This study may be where this information of 3-4 hours comes from. It shows that people who nibble/graze have the same level of carbohydrate and fat oxidation during the day. There is no “spike” in metabolism or carb or fat oxidation, it’s pretty much the same all day. People who eat 2/3x a day have peaks, which are compensatory. For example, carbohydrate oxidation is increased after first meal (hearing “breakfast is the most important meal” anyone?) and was decreased over the fasting period (last meal of the night to first meal in the morning). HOWEVER: during the time your carbohydrate oxidation is low, your fat oxidation is HIGH to compensate for energy. So while breakfast proponents tout that your carbohydrate oxidation is low and you need to boost it, they kind of ignore that your fat oxidation is high to compensate. Your body is a well oiled machine guys!

Moral of this story? As long as you eat in a deficit, it doesn’t matter how many times a day you eat. Your metabolism doesn’t “boost” when you eat multiple times a day. Your BMR is your BMR whether you eat 100 calories every 2 hours or a few 500 calorie meals a day. My take? Eat when you’re hungry. It’s a crazy concept, but do it.

July 4, 2012 Metabolism Series, Myths, Nutrition, , Read more >

If I skip a meal or don’t eat for over 12 hours, will my body go into starvation mode?

Oh, starvation mode: how I loathe thee! What does starvation mode even mean? I googled it. Wikipedia says it’s the body responding to long periods of low energy intake. So what is a “long period”? During the fasting study from before we found that it took more than three days of ZERO food for your metabolism to drop 8%. 8%! That means your BMR goes from 1450 calories a day to 1334 calories a day. But we’re not talking about zero food now – we’re talking about less than optimal food.

Let’s go back to the Minnesota Semi-Starvation Study. These guys were fed 50% maintenance for 6 months and their BMR dropped 40%. However, their weight loss never stopped. They hit 5% body fat (rock bottom in men, basically unlivable in females) without breaking stride. At no point and time did their body simply STOP losing weight and “cling” to fat. Yes, their BMR decreased by 40%, but as long as they were eating at 50% maintenance (say maintenance was 2,000, they were eating 1,000. When it dropped to 1900, they ate 900, etc.) they lost weight. It didn’t stall, their body fat didn’t magically increase. Yes, eating below your caloric needs slows down your BMR, but there is never a time where the body magically decides to live off nothing. It’s efficient, but if it were that efficient no one would die of starvation.

So, how much does your BMR decrease? And when? Is there a magic number, like the 1,200 calories a day most would have us believe? This study put women on a mean intake of 490 calories/day. The study is a little iffy because some of the women “cheated” – something I’ll cover in my final post in this series. Anyway, after losing 19kg the BMR of these women dropped 21%. So, if your BMR was 1450, it’s now 1146. The study suggested that this was due to a loss of lean body mass. You know the adage that muscle burns more calories than fat? It’s true. Losing muscle by fasting/lowering your intake below basic needs will eventually cause a loss of muscle and decrease your BMR. The study suggested that lowering your caloric intake enough to lose fat but not muscle would be ideal.

But how do you do that? Cardio?

This study took obese women, fed them 800 calories a day, made them take a spin class that put them at 70% exertion (as in hauling ass) a few times a week and tested their BMR. They became more fit (as in their VOMax increased), but their BMR didn’t really recover. So while it had a short term affect on their metabolism, it really did nothing to stick around.

What about weight training?

This study took a group of people who did cardio plus an 800 calorie diet vs. a group that did strength training and an 800 calorie diet. The cardio group lost more weight, but they lost more lean body mass than the strength training group. In fact, the group that did strength training had an INCREASE in metabolism over the non-strength training group. Their lack of weight loss was attributed to their body burning fat and building muscle, whereas the cardio group just lost weight both in fat and muscle. Moral of this story? Weight training increases muscle, which increases your BMR, which means you lose more fat than muscle, which means your BMR doesn’t tank like it does on just cardio.

Alright, so I strayed off topic a bit with this exercise business and BMR and stuff. Let’s get back to the crux with a great question: Can you fast for a long period of time and lose weight?

Get ready for this: yes. 

Don’t try this at home! A 27 year old, 450+ pound man was put on a fast for an entire year (382 days). Scientists supplemented him with the necessary electrolytes, but otherwise he ate no food. Zero. Zip. Zilch. Nadda. What happened? He got down to 190 pounds. How much of it did he gain back? 15. Now, 5 years after the study, he hovers around 197-ish pounds. On average.

Does that look like he clung to any fat to you?

July 4, 2012 Metabolism Series, Myths, Nutrition, , , Read more >

If you don’t eat, does your body eat your muscle or fat first?

As expected, this is also false. It shouldn’t be a surprise to anyone – it just doesn’t make sense. Off of the top of your head name some important muscles: heart, diaphragm, right? These are necessary to our life. Without them, we don’t function. Why would your body go and target these areas BEFORE going and eating away at fat? After all, stored fat has more energy than muscle (over twice as much, actually) and when was the last time you called someone “starving” because they had only fat and no muscle on them? That’s right, you didn’t.

So why do we continue insisting that our bodies are somehow programmed to preferentially break down our muscles over our energy rich fat? I think Alloran on Fitocracy made the best analogy – “Why tear apart chairs, tables, bed frames, etc. to build a fire when there’s a pile of firewood just outside the door?”

But I wouldn’t call myself Bill Nye with a vagina is I didn’t throw some science at you.

During a two day fast you have a 5 fold increase in Growth Hormone. Growth hormone is what tells the body to conserve protein and therefore muscles. More GH, more protein conservation. GH is a jack of all trades, though, because this badass chick also promotes lipolysis. For those of you who need a Latin reminder, lipo = fat lysis = killing or destroying.  GH kills fat and saves protein.  I told you she was a badass chick.

Growth Hormone isn’t the only big bad chick proving that you burn fat during fasting. Glycerol (released when the body breaks down stored fat) and palmitic acid (also found in fats) are high in the plasma during the first 12-72 hours of fasting. In fact, they double.

But if there’s so much science – and common sense – showing that you don’t lose muscle preferentially, where did it come from? Turns out a few studies showed a decrease in lean body mass (muscle) during a fast. Don’t worry, new science helped to remedy what may have been a misunderstanding. Turns out that majority of the “weight loss” from muscle was a loss of glycogen and water. Glycogen, for you non-bio nerds, is the stored form of glucose. So most of the loss of “mass” from muscle was water and stored glucose. Additionally, these same studies showed that about 14% of the energy from a fast came from protein, whereas 85% came from stored fat.

So no, skipping breakfast, participating in IF, or even lying on the couch all day not eating because you’re sick and lazy won’t cause your body to eat your muscles away. It just doesn’t make sense.

July 4, 2012 Exercise, Metabolism Series, Myths, Nutrition, , , , Read more >

Do you need to eat before you workout?

So this one is a slippery slope, because we hear two sides of this. I’ve heard not to eat before the gym and I’ve heard to eat before the gym. It’s also a slippery slope because not everyone is looking to get the same thing out of their exercise. Some people want to get jacked and bench press their boyfriends, other people want to run at least 50 miles that day. As you can probably guess, depending on your needs depends on the better answer. So I’m filing this as “Maybe kinda sorta depending” true/false.

Let’s start with my fellow meatheads. When I go to the gym I want to up my lifting and eventually be able to deadlift my boyfriend, then possibly clean and jerk him if we’re attacked in the wilderness (let me pretend gaining strength is everyone’s ultimate goal, mkay?). Anyway, I want anabolism. Yep, anabolism, like “anabolic steroids.” Anabolism = building, catabolism = breaking down. So I want muscle anabolism to be at an all time high. If you skip breakfast and say go to the gym on a 12-16 hour fast, is that good or bad?

Turns out you’ve gotta be smart about it.

This study shows that if you fast, do some gnarly strength training and then down a solid breakfast you have INCREASED anabolism. Other studies found that people who fasted and those who didn’t had the same level of physical performance, at least in strength training.  In fact, you can fast for 3.5 days and have similar levels of isometric strength and anabolism.

But, like other articles before, it’s not all rainbows and sunshine. These studies only studied people who exercised for 90 minutes. I know I have a lot of runner followers that punch out 4 hour runs a few times a week. That’s a bit more than 90 minutes, right? The fasting studies are contraindicated for marathon runners. This study took runners after a 27 hour fast and made them run at 70% maximal O2 uptake, then made them try again 3 hours after a meal – at random. Results? “Fasting caused a 44.7 +/- 5.8% decrease in endurance.”  Other studies have found much the same – marathon, endurance, long distance, etc. runners have a huge decrease in performance if they fasted before exercising.

Depending on what you want from your workout and the length of your workout depends on whether eating beforehand or not will influence your workout. Looking to build strength or working out for less than 90 minutes? Pre-exercise meal isn’t necessary. Is today your long run day? Definitely best to fuel up beforehand.

July 4, 2012 Metabolism Series, Nutrition, , Read more >

Fasting, cheating and other big bears

So this entire series has focused on the myths around your metabolism. I’ve shown that you don’t need to eat every few hours, that you can exercise fasted, that you can fast, that low calorie diets won’t kill all your muscle…but I’ve forgotten an important aspect of all of this. Even though I consider myself an uber-nerd scientist first and foremost, I do understand and acknowledge that there is an element most of us nerds forget: the human element. If it were as easy as fasting once a week, exercising, eating into a deficit to lose weight, wouldn’t everyone be strutting around Kate Moss style? There’s obviously something missing – and I’ve hit on it before, but now I’m going all in baby.

Not eating sucks.

Yep. Not eating sucks. Not eating a giant slice of cheesecake even though you want to makes you crave cheesecake. I showed before that it takes like 5 freaking weeks for your cravings to diminish on low calorie diets. Plus, one of the studies I cited was a little iffy because women cheated! CHEATED! You’re in a scientific study and you can’t adhere to a diet? This is what I call the “Human Element of Science.” It’s the part where your brain tells your body something that may or may not be true.

How about the craving studies? Let’s put this together. You’re on a low calorie diet. To meet all your nutritional needs, you need to eat food that is high in proteins and vitamins – this means no cake. You crave cake. You WANT cake. You crave cake for 5 weeks. Your friends are all going out to eat dinner at your favorite restaurant – the same one with the 400 calorie drinks you down like water – so you can’t go. Your social life starts to disappear because you have a strict diet to adhere to, all while juggling cravings and – depending on how low calorie a diet you have – an eventual decrease in metabolism. Sounds like a crappy way to go.

What about hunger? If your body only “needs” a certain amount of calories, why do people overeat? I’ll compare two studies from before (http://www.ncbi.nlm.nih.gov/pubmed/19943985 and http://www.ncbi.nlm.nih.gov/pubmed/18053311). One study measured the hormones that tell you you’re hungry and found that eating twice a day had the same level of both as those who ate three times a day. However, the second study ASKED people if they were hungry, and people who ate 2 times a day SAID they were hungry more often than the people who ate 3 times a day. Notice the difference? I’m sure a psychologist could delve into this super deep and tear apart why someone may THINK they’re hungry despite biological evidence showing them that they’re NOT hungry, but I think you and I can guess pretty accurately. When noon rolls around my stomach growls, regardless of how many cupcakes I downed between breakfast and then, because it’s time to eat. Am I hungry? There’s no possible way. This is the human element.

And, last but not least, my favorite study – the Minnesota Semi-Starvation Study. After 6 months of this restrictive diet the men became crazy about food. They thought about food a lot, planned their meals, thought about food, talked about food…their life revolved around food. This is a dramatic change from their original personalities. They binged, hoarded, became recluses…it created an unhealthy relationship with food. I think a lot of us can relate to this. I’m sure we can remember – with sad fondness – times when we didn’t know the calorie content of every food or times when food was just food. Dieting can change all of this.

So while I can parrot out all these cool sciency-facts about losing fat by not eating over maintenance and low calorie diets and blah blah blah I’m ignoring the fact that this really doesn’t work for everyone. We have lives, needs, preoccupations, etc. Losing weight is tough. It can be lonely, bland and obsessive. Without adding your own “Human Element” into these facts you’ll find yourself no better off than the Minnesota Semi-Starvation Study men: dreaming of food instead of sex.

July 4, 2012 Metabolism Series, Science, Read more >