I'm currently using the Slow Carb Diet to lose some weight. I find that it works well, but I plateau often. I'm trying (and succeeding but ever so slowly) to get under 15% body fat. Been doing it a while and it's fine.

I find that if I'm dropping weight I get light-headed. Well, it's not really the same feeling as "must eat now" so I'll call it 'fuzz-headed'. For instance, on cheat day (Sat), I'll feel fine. Likewise Sunday. But by Thursday (today) I feel sorta light headed / spacy / fuzzy. I'd say it is similar to being half hung over, half low blood sugar.

Important note: I doubt it's blood sugar. I've tested my blood sugar (with a strip kit) about 8 times when I've had this feeling and it's always been in the 95-130 range. My appetite doesn't seem to have anything to do with it -- my hunger levels are usually pretty low when I'm experiencing this fuzz-head feeling. Also, I don't think it's hydration, judging by urine color. I drink about 48oz of water (coffee, tea) between 7AM and 5PM and never feel thirsty. I have talked to a Dr about this and he tested my blood... something... levels. Slightly elevated creatinine (sp?) but all else normal. He thought the creatinine wasn't anything to be concerned about.

A typical day looks like this:

  • 7AM: protein shake, 45g protein, 16 oz water, flax seed
  • after 7AM: 2 cups coffee, black
  • 9:30AM: fuzzy headed feeling starts about her
  • 10AM: breakfast: 4-6 oz pork or chicken, 1/2c lentils, 1/2c spinach, 2 eggs
  • 2PM: lunch: 1.5c slow carb chili (kidney beans, beef, vegetables)
  • 5PM: fuzzy headed feeling has been with me from 9:30 until now.

I've tried attacking this issue with vitamins (Vit D or a multivitamin), no effect. I do find it will go away if I get a solid half hour of aerobic activity like hill-walking or swimming. Large doses of caffeine will clear it up as well (20 oz coffee). I want to avoid caffeine because it disrupts my sleep. Getting an hour in at the gym in the morning is difficult.

My questions: could this be related to the weight loss? Like as I'm shedding fat there's some sort of byproduct that gets stuck in my blood and my kidneys aren't filtering it out well? Could this be a specific nutrient that I'm not getting enough of (esp. something that a typical multi wouldn't take care of)?

I've asked about this on the SCD forums in the past but really didn't get a good answer. Hopefully the SE network will give me better results.

  • You have never asked your doctor? Feb 3, 2012 at 18:33
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    @Aaron: it's in there, read it again.
    – jcollum
    Feb 3, 2012 at 18:48
  • I see it; was under the impression that you spoke to the doctor about the blood work in a general sense. Have you stopped consuming caffeine for any length of time (2+ weeks) to see if it clears up? Feb 3, 2012 at 18:54
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    @jcollum are you eating any fruits(sugar)?fat?i do not see sugar/fat in your diet. Even if your blood test showed normal sugar levels, weight loss with gym training makes hormonal imbalance (which will make you feel the way you feel) if you do not get proper nutrients.You DO need a bit of sugar AND FAT(the good fat, since fat will regulate the bodily hormones). Aim at having omega 3 fat and Potassium(best two sources of potassium are dried apricots and bananas). try that and see if it feels different
    – ccot
    Feb 29, 2012 at 18:50
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    @jcollum it's up to u, but why not give it a try to see if it helps? a bit a fruit is also healthy(in addition to getting sugar from them)
    – ccot
    Feb 29, 2012 at 19:56

3 Answers 3


Perhaps the two coffees prior to breakfast could be the reason or your lightheadedness. On diets where carbs are limited we rely on ketones made from adipose tissue to fuel our bodies. However I remember reading several articles stating that the coffee can inhibit the rate at which our body uses fat as fuel. Therefore, causing a lower blood sugar after breakfast when our body should be releasing a steady stream of ketones in the blood.

I would attempt to remove the coffee for a week or two and see if there is a noticeable difference.

  • Whew... yeah? That'd be... difficult. Got a link that I can check -- a study of some sort? I don't want to bite off that kind of pain without a good reason.
    – jcollum
    Feb 3, 2012 at 20:58
  • I've spent 20 minutes reading various posts about this on the web and I've come to the conclusion that there's a lot of conjecture and very little actual info.
    – jcollum
    Feb 3, 2012 at 23:00
  • That being said, this is the best theory to fit the data that I've seen. I suspect I'll cut the coffee and tea (and there's plenty of both) out of my diet for 2 weeks and see what happens. Would like to see a reference to an actual study if you have it.
    – jcollum
    Feb 4, 2012 at 0:51
  • I believe the mechanism is that caffeine causes our body to release insulin, therefore blunting the fat releasing processes of glucagon (insulin inhibits glucagon) and also results in low blood sugar due to an increase insulin release and already normal sugar levels. I will find the article the info is from.
    – zach
    Feb 4, 2012 at 1:25
  • TLDR: Nope, didn't work. I've dropped my caffeine levels significantly (only decaf coffee, except on cheat day). No impact on my light headed feeling (it's hitting me strong right now, probably because I'm in ketosis). My total caffeine intake is about 1/4 cup caffeinated coffee per week.
    – jcollum
    Mar 15, 2012 at 17:43

I've experienced that feeling before, when I was a student in college. It was related to not having enough to eat (for monetary reasons). Unfortunately, there is quite a number of causes of those symptoms that can range from:

  • Body needs adjusting to lower carbs (quite likely)
  • Insufficient food (low blood sugar)
  • Normal byproducts/waste built up in your fat stores that get released at once

If this is a drastic change from the way you have been eating, then there is a period of adjustment your body has to go through to work with the type of food it is getting. If this is a serious caloric deficit (like 1000 Calories), your body may never get used to it.


A possible answer is that you are not getting enough sleep.

Personal experience is all I really have to support it. When I've experienced this type of feeling, it is primarily when I'm coming off of a not-so-good period of eating and my body is adjusting again to not having a lot of sugar/other carbs. But I do find that it is more often if I'm not getting enough sleep, a good "catch-up" night or two of more sleep than I usually get seems to help my body adjust.

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