Tag Archive: fasting

A Case Against Breakfast

Let me preface this article by saying “If you’re hungry, you should eat.” Plenty of people wake up ravenous, enjoy breakfast, and go on with their day. Others wake up without an appetite and report that when they do eat breakfast, they feel like crap all morning, or they’re hungry twenty minutes later. Without delving into the “What are you eating? How much? Etc” argument, I’d like to present this little piece of science for those of you who want it. If you find breakfast a chore here’s some ammo to shoot at the pro-breakfast crowd always trying to get in your face. If you’re not hungry, you’re not hungry: end of story. Every body is different.

Let’s start with hormones and waking. Cortisol (click the link to read about it) is a huge part of your sensation to wake up. It gradually rises through the night, and reaches its peak when you open your eyes. Your cortisol is highest in the morning and may continue to rise after you wake up, until about 30-45 minutes later. That’s breakfast time. Here’s the deal with cortisol – it antagonizes insulin. Insulin helps pull the sugar from your bloodstream after a meal and put it into your cells to refuel them. Because of this, you end up with a higher blood sugar than you would normally.

The issue is that with a blunted insulin response your cells aren’t getting the energy they need. Simply put, insulin gives the energy directly to the cells, and cortisol gets in the way of them doing that. If your cells are yearning for energy they’re going to send hunger signals to your brain to encourage you to eat and feed your cells. This is the case with people with chronically elevated cortisol levels as well who have trouble maintaining a normal appetite.

What about the fit person?

A fit person will have increased insulin sensitivity, especially as they lean out. They tend to be very responsive to an increase in blood sugar and quick and efficiently pump out insulin to compensate. These people then see their blood glucose drop faster, and tend to get hungrier faster. This is exacerbated in the fasted morning states with a high cortisol. You have an extremely active pancreas pumping out insulin and being countered by cortisol, so you’re pumping out more. This can mean a dramatic decrease in blood glucose. Not so much as to cause hypoglycemia, per se, but enough for your hunger signals to fire up just a short time later.

But why does this not affect ALL people – why are some people breakfast lovers and others aren’t? The level of cortisol in your blood is highly dependent on a lot of factors. Some people simply do not have a high enough level of cortisol to counteract any of the breakfast-induced blood sugar problems. Others, such as diabetics, have a need for a regular blood sugar management. Every individual is different, which is why I say again – if you’re hungry, eat!

Lastly, let’s look at a very specific study targeted at the traditional “If you skip breakfast you’ll gain weight” hoopla. This study was a 16 week controlled study in overweight and obese adults, one group ate breakfast, the other didn’t. Between both groups the average weight loss was 1.18 kgs vs. 1.17 kgs. Essentially, the results showed little difference in weight loss between breakfast eaters and non-breakfast eaters.

So, as I said earlier – eat if you’re hungry, don’t eat if you’re not. If you find breakfast is detrimental to your state of mind (no one likes being ravenous at 9am!) then skip it. It’s your individual choice.

August 6, 2014 Fat Loss, Myths, Nutrition, Science, , , , Read more >

How long until my metabolism drops from fasting?

I think I know where this information came from – The Minnesota Starvation Study. Matchstick Molly does a great breakdown of this study, but in essence they took a bunch of middle aged, totally healthy guys and over the course of 6 months studied how they responded to a diet that was 50% of their daily intake needs. Basically, if the men required 2,000 calories a day to survive, they put them on 1,000 calories a day. What did they find? Their metabolism decreased by 40% – something that stayed that way for about 8 weeks after normalizing the diet. But this is a topic for another part of the metabolism series, so we’ll come back to that. This “fact” is talking about fasting after all!

How long does one need to fast before their BMR (basal metabolic rate, i.e. the amount of calories it takes you keep you alive if you lay in bed all day and don’t move) drops?

This study found that after 3 days of starvation (i.e. no food, just water) your metabolic rate INCREASES, in fact by about 1 kJ/minute (1kJ = .239 calories). This study also shows the same thing – 36 hours into the fast the BMR INCREASED, at 72 hours the BMR was about the same as it was 12 hours into the fast.

It’s not all roses and sunshine though – this study took a few healthy weight females and put them on a 48 hours fast, then measured how they responded to refeeding. It showed that 40-90 minutes after being fed after the 48 hour fast their body had a decreased metabolic rate. This means the thermogenic property of food (covered in future articles of this series) wasn’t as high as it was in other people who didn’t fast. Still: no 40% decrease in metabolism after 12 hours of fasting.

When does your BMR decrease, though? I mean, it can’t just rev and rev away, otherwise you’d die ASAP.This study shows an 8% decrease after 74 hours. So it took 3 days of ZERO food for your BMR to drop a measly 8%.

Another study for your reading can be found here. This one found your BMR increases 3.6% after a 48 hour fast. This is old hat now- you guys know this. BMR increases, then decreases after 74 hours by 8%.

Moral of the story? Your BMR will initially increase during the first 3 days of fasting by about 3-4%, then it will decrease 8% after 3 days of fasting.

I’m calling this “40% decrease in metabolism after 12 hours” a big fat FALSE.

July 4, 2012 Metabolism Series, 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 >