What actually causes the BMR to drop with dieting and fasting?

metabolism
(VLC.MD) #1

When losing weight with Keto or fasting … your bodies responds by reducing your BMR (Basal Metabolic Rate)(aka “metabolism”). Paraphrasing Dr. Fung, “Your body ain’t stupid … when there is less calories in … it doesn’t keep the calories out the same.”. Whether or not fasting reduces your metabolism less than calorie restriction (which is might) is another matter.

What I am in search of … ?

What exactly changes to drive your metabolism ? Does it involve thyroid ? Will free T3 and free T4 drop with weight loss ?

All information / advice appreciated !

(Bacon is a many-splendoured thing) #2

When you cut calories (“semi-starvation”), the body thinks there is a famine and hoards fat. It compensates by reducing your metabolic rate. Fasting, on the other hand, does not seem to trigger this reaction.

If you are fat-adapted and eating a well-formulated ketogenic diet, you should be eating fat to satiety, so you will not be restricting calories at all. Your body might tell you to stop eating sooner than you might expect, but it will be satisfied with the level of food intake and will not feel any need to hoard fat. The key is to eat until you are no longer hungry, and let your body tell you where that point is, regardless of how many or how few calories you might be eating. There is a documented case of one participant in a low-carb, high-fat diet study who ate around 3500 calories during the study and still lost body fat.

(VLC.MD) #3

I’m interested in what changes when someone’s BMR does drop.
Ideally measurable things.

Let’s say someone ate 1000 calories of potatoes a day for a year.
And it caused their BMR to drop.

What changed in this person ?
What hormones changed ?

#4

http://www.shapingconcepts.com/blog/hormones-that-control-your-metabolism/

(VLC.MD) #5

Thanks. Good starting point.

Regulating thyroid hormone levels is the cornerstone to keeping your metabolism running on high.

The main cause of metabolic slowdown is a decrease in active thyroid hormone. There are three main reasons why thyroid hormone levels will go down.

Very thyroid centric ideas.

  1. The loss of lean muscle
    A good point. And measurable. Less Lean muscle = likely lower metabolism.
  1. Increased production of cortisol
    When the cortisol receptors on the pituitary gland are activated, they reduce production of thyroid stimulating hormone (TSH)
    Cortisol also affects the conversion process of T4 (circulating thyroid hormone), to T3 (the thyroid hormone that hooks up to the receptors).

Outcome: Lower TSH, Lower T4, even lower T3

  1. Increased production of insulin
    The resulting over-secretion of insulin causes cortisol levels to rise which as you just learned can reduce thyroid hormone production.

While dieting, insulin overall should be down. Unless you are increasing your carbs and protein (ie low fat diet). Insulin should be dramatically down on LCHF/Keto/Atkins.

Measurable list so far

  • TSH (Thyroid Stimulating Hormone)
  • Free T4
  • Free T3
  • T4
  • T3
  • cortisol
  • insulin (fasting vs non-fasting)
  • Lean muscle mass.

insulin is so variable (depends on what you recently ate) … fasting insulin is the only useful thing.
TSH is highly variable (it is a secreted in a pulsitile fashion) so wouldn’t be a reliable marker for BMR.
Muscle mass - I think this would be a reliable and relatively easily measured marker.
Free T3 - of all the thyroid indices … this one might be the best.
Cortisol - probably important, but it varies so much (like TSH) … hard to know the usefulness.

The article brings up an excellent idea … can Metabolic Rate be easily measured ? I assumed the answer was “not really”.

A good starting point to assessing your metabolism is through a metabolic profile assessment. Shaping Concepts is a provider of this metabolism test through the use of the Korr Metacheck analyzer.

  • not sure if this is useful (ie actually works). But the link to it is dead ! (probably prophetically).
(VLC.MD) #6

Slight topic change … to hone on what I am searching for (if it exists).

OLD: What actually causes the BMR to drop with dieting and fasting?
NEW: What measurable things are proportional to the drop in BMR with dieting and fasting ?

Feel free to compare and contrast which measurable things may change more or less with Keto vs Fasting vs Low Fat.

#7

Great questions!

(Jason Fletcher) #8

When the body does not have enough energy from food or being taken from the body’s fat. It will lower BMR in attempt to save energy. Lower BMR can happen when there is no body fat or your body cannot metabolize it properly do to metabolic disorders. For example when you go on a calorie deficit and you are insulin resistant your body will not be able to use fat efficiently until you lower insulin. If you are eating low calorie carbs all day you will be keeping insulin elevated and your body will also be demanding more energy. But will have a hard time getting it from your fat cells. The body will still be able to produce energy from GNG but this will be at the sacrifice of your lean muscle mass. But by being in this state your body will lower your BMR. You most likely will be very hungry and lethargic as well. By eating keto you lower insulin allowing the body to use fat properly. Plus reducing the demand of GNG from your lean muscle. And since energy needs are in balance you will be able to maintain BMR. Since with fasting there is no insulin raised from food. You are able to tap into fat the same way you do with keto. Just it will take longer since if you are not keto adapted to burn fat your body will still struggle still to meet its needs. Some of these pathways can take up to 3 month to develop while eating ketogenic. In most cases in about 3 days into a fast your body will adapt to some point leaving you feeling less lethargic.

(Jason Fletcher) #9

This you can test a VO2max.
When a person adapts to a exercise such as running there muscles will become more efficient over time and will require less energy to preform that task. This can be measured in the VO2max. This is one of the reasons for raising BMR when trying to lose weight using HIIT workouts are better. Your body does not adapt as well so you will burn more energy. Everyone wants a higher BMR. But a Higher BMR in most cases is just your body being inefficient. Your body will always try to adapt to use less energy for the work required to do the job. By lifting weights and doing HIIT workouts you increase the demand for your body to be capable of higher levels of energy use. So these workouts increase BMR because the pathways required to use more energy when active require more energy when inactive.

#10

I wish this was always so. I think it may not be true for everyone, however, because so many keto dieters struggle with slow or stalled weight loss. Very often we turn to fasting (intermittent or extended) to start losing weight or break a plateau. For some of us, even that doesn’t seem to be enough.

(VLC.MD) #11

Are you saying get
Fasting glucose and insulin
1hr glucose and insulin
2hr glucose and insulin ?

Or just 1 fasting insulin and 3 glucose readings ?

(Carpe salata!) #12

The 3 glucose is the basic GTT. ‘With insulin’ usually means 3 insulin readings as well. That’s what I got and it gives more info ie your insulin spike ( mine was a bit high) and your insulin recovery ( mine was ok) .

They might think it’s a pain because they need to collect separate vials each hour apparently.

(Bacon is a many-splendoured thing) #13

I just remembered some research I read about (probably in Taubes or Teicholz) that elucidated the role the vasovagal nerve plays in appetite and fat regulation. Tumors in certain spots in the thyroid can also have an effect on this regulatory process, so obviously the thyroid plays a role as well.

(Carpe salata!) #14

Yup there are a lot of related factors. Blood sugar level, ghrelin hormone, stomach stretch, food visuals, time-of-day habituation, etc. sometimes you might have certain foods that make you feel ab it blergh. Use those to advantage.
Drink more water.
Have your self-talk patter ‘sugar is poison’ ‘do not want’ …
I like ‘do not want’, it has a lot of subtle meaning

#15

[quote=“Darcy, post:10, topic:19878, full:true”] Very often we turn to fasting (intermittent or extended) to start losing weight or break a plateau. For some of us, even that doesn’t seem to be enough.
[/quote]
Are you saying that there are folks who don’t lose weight while doing an extended (water) fast?
Really?

#16

Speaking from my own experience, I do lose weight during the actual fast, and some of it is apparently actual fat, but once I get back to keto eating again (even though my eating days are IF and keto), the weight comes back (and sometimes brings friends). I may be uniquely messed up, because of type 2 diabetes/severe insulin resistance. The longest I’ve fasted in 7 days in a row, but I wonder what would happen if I did a whole month? Could it possibly all come back? I guess it could.

#17

No doubt, some of us have a steeper metabolic hill to climb than others. :slightly_frowning_face:
I could see how someone who lost 5-10 lbs during a short fast might gain it all back when they resumed eating. I’ve gained 5 lbs overnight, just water. But if 15-20 lbs were list during an extended fast, I would think most of that would stay off with proper nutrition.

(Doug) #18

Darcy, you really do present a puzzle, and I salute your good attitude, considering how frustrating this kind of thing tends to be.

Yes, it could possibly come back, but after a month-long fast, that would require substantial storing away of food energy by the body, and unless you were eating way beyond your caloric expenditure, I just can’t see it. I know that sounds like “calories in/calories out”…

#19

Thanks Doug, you are a great cheerleader and kind to put up with all my rants about my problems. :slight_smile: When I’ve added up the calories, I do eat pretty high on eating days, definitely over 2000, usually more like 2500 (and above), just because of the liberal use of heavy whipping cream, butter, parmesan cheese, avocados and the like. Now I am subtracting the HWC, which is not fun but that might account for going over on carbs sometimes and a lot of liquid calories. I would have thought that eating high fat and on the high side for calories would not be a problem on eating days. It could not be enough to add pounds even if following KICO. Also, I do attribute to 20-25 pounds of lasting weight loss to keto, IF and EF. But it has not had the weight loss effect for the past few months.