Tag Archive: science

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 >

Do you have to “Eat Clean” to lose weight?

One of my major pet peeves is when people tell you the reason you’re not losing weight is because you’re not “eating clean.” What does “eating clean” even mean? You can buy a ton of books on these “lifestyle changes” that involve cutting out sugar, soda, sometimes dairy, sometimes fruit, anything processed, etc. For some people that is hell on earth – you cut out 99% of some peoples diet. I can understand why people tell you this. It’s a lot easier to lose weight when you’re eating cups and cups of spinach (which can be like 20 calories a cup) versus downing a whole 1,200 calorie pizza in one setting. But do you really NEED to eat clean to lose weight?

No. And if someone tells you that, slap them with some science yo.

First, let’s look at the nutrition professor who lost 27 pounds in two months eating just Twinkies, Hostes cakes and other gooey treats. He took a multivitamin and had one protein shake a day, but otherwise he ate Cartman-style meals for 2 months. And lost weight. And improved his cholesterol. His only requirement was to eat 1,800 calories a day or less. Considering his maintenance caloric intake is about 2,500 (according to him) this was enough to cause a serious deficit conducive to losing weight. He. Lost. Weight. Does he recommend this diet to anyone else? No, he doesn’t. He makes an important point though – some people in poor states live like this day in and day out. They only have access to a convenience store and there’s no grocery store for miles. I did an article on this, so you can read it here.

There’s also a marathon runner who sent a PR of 2:34.14 after eating nothing but McDonalds for 30 days. Spoiler alert: he lowered his cholesterol too. (If this freaks you out, google some articles about how Morgan Spurlock’s “Supersize Me” is kinda a total scam)

Now you’re asking, where’s the science? This is just some dude eating crap and losing weight, big deal. Don’t worry. There’s been a TWO YEAR study comparing diets of groups of people by changing their macronutrient intake and showing weight loss over this time. Some people ate only 15% protein, others 40% fat, etc. They wanted to know if the amount of calories you ate were more important than what you ate. Guess what? Calories won. It flew in the face of previous studies that only lasted 6 months or less testing various diets (Zone, Atkins, etc.) on different people. Long term calories are all that matter.

Now, I know what you are thinking. Losing weight =/= health. And you’re right! It doesn’t! These studies don’t take into account building muscle and needing adequate protein, or meeting your daily vitamin nutrients, or any of that fun stuff. However, this series is about metabolism and losing weight, so I’ll assume you all know this.

So no, you don’t have to “eat clean” to lose weight. Calories are king. Do you eat clean because it keeps you fuller longer? Because you genuinely enjoy vegetables and fruits? Is eating cleaning turning out to destroy your social life? Ask yourself these questions before you buy into this idea that you can or cannot eat certain foods in order to lose weight.

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