Wednesday, January 09, 2008

Fasting for Weight Loss and its Effect on Blood Sugar

In the last couple days I've received a number of emails and posts about using short periods of fasting for weight loss and its effect on blood sugar.

In a post to my blog I was told that a couple people who are diabetic have been using short periods of fasting with a lot of success and have actually been able to lower the dosages of their medications.

I also received an email from a personal trainer who wants to use Eat Stop Eat with her clients but is worried about the effects that using short periods of fasting for weight loss would have on blood sugar levels. Mostly, she was concerned about hypoglycemia.

Throughout the 24 hour cycles of eating, digestion, and fasting, the amount of glucose in your blood is generally maintained within a range of 70-140 mg/dL (3.9-7.8 mmol/L) as long as you are healthy.

Hypoglycemia is another way of saying "low blood sugar". While many people claim to suffer from low blood sugar, as little as 5-10% of the population actually have a malfunction in their ability to regulate their blood sugar levels. There is no actual "cut off" value for blood glucose levels that truly defines hypoglycemia for all people and purposes.

Research in healthy adults shows that mental efficiency declines slightly but measurably as blood glucose falls below about 65 mg/dL (3.6 mmol/L). However, the precise level of glucose considered low enough to define hypoglycemia is dependent on the age of the person, the health of the person, the measurement method, and the presence or absence of negative effects.

According to the research on using fasting for weight loss, a 24 hour fast should not place you into a hypoglycemic state, and I have not seen any research that has shown a subject going below 3.6 mmol/L blood sugar during a short term fast. However, I'm the first to admit that there is a difference between research and real life, so I decided to experiment on myself.

I took blood glucose measurements on myself during a 24 hour fast. It's important to note that this investigation only had one subject (me) and that testing hypoglycemia with the finger prick technology is prone to misleadingly low numbers. Nonetheless, I couldn't help but be intrigued with what I may find.

(Good for research, bad for my fingers)

I started my experiment at 1:10 pm with a Bowl of Chili, a whole wheat bun an old fashion dip donut and a large coffee with two cream and one sugar, all courtesy of my friends at Tim Hortons ( ~750 Kcals, 40 g fat, 70 g Carbs, 30 g Protein)

I began measuring at 2:15, exactly 45 minutes after my last sip of coffee. The first numbers are my blood glucose in mmol/L, the number in brackets is my blood glucose levels in mg/Dl.

2:15 PM TUES- 5.9 (106.2)

4:15 PM TUES- 4.8 (86.4)

6:15 PM TUES- 4.4 (79.2)

8:15 PM TUES- 4.3 (77.4)

10:15 PM TUES- 4.6 (82.8)

12:15 AM WED- 4.0 (72) (Bed Time)

3:15 AM WED- 4.4 (79.2)

6:15 AM WED- 4.7 (84.6) (Right after I woke up)

8:15 AM WED- 4.6 (82.8)

9:00 AM WED- 4.4 (79.2) (A little bit of hunger here)

10:15 AM WED- 4.1 (73.8)

12:15 PM WED- 3.9 (70.2)

1:30 PM WED- 3.9 (70.2)

At 1:30 I ate my first post-fast meal, which was supposed to be a small chicken salad, but unfortunately it was a 1,200 Kcal Bomb of a salad from Boston Pizza (1,200 Kcals, 86 g Fat, 45 g Carbs, 62 g Protein)...My mistake, I was at a business meeting, but still, I should have known better.

Twenty minutes after finishing my heart attack of a salad, I started recording again.

2:00 PM WED- 5.9 (106.2) 20 minutes after my last bite

2:20 PM WED- 5.8 (104.4) 4o minutes after my last bite

2:45 PM WED- 4.8 (86.4) 65 minutes after my last bite

4:45 PM WED- 4.4 (79.2)

The interesting things I learnt from this study were that my feelings of hunger were not related to my blood sugar levels, nor was any feeling of light-headedness.

I was also very surprised that despite the massive amounts of sugar, my blood sugar never went above 6, and dropped pretty quickly after my meals. It stayed pretty tightly controlled between 3.9 and 5.9.

All in all, this experiment showed me that while I am fasting my blood sugar stays within the normal range. I will repeat the experiment during my next fast and study what happens when I workout while fasted.


Stumble Upon Toolbar


Carrie said...

Thanks for addressing this, Brad.

I would be very interested in seeing more studies on this, if you've got them at hand. If not, I'll get around to it, but not til after my thesis is written :)

Brad Pilon said...

Hi Carrie,

I'm going to conduct more "trials" on myself and some friends.

There's lots of research on fasting and blood glucose. However, since research is always conducted on subjects who have been screened for any underlying health issues, its always fun to double check with real world, real living peope.

I'm fasting now, and plan on training tomorrow from 11 AM till 12 PM, so at hours 22-23 into my fast.

Shoud make for some interesting numbers.


Brad Pilon said...


Forgot to mention, good luck with the thesis!!


Nawaz ALi Lakho said...

I really like this blog… Just some info for some of the other readers who are serious about losing weight. I used the Fatlossity System and I can definitely recommend it. I lost 18lbs in 6 weeks and am still going strong...

Anonymous said...

The ban on the sale of the weight loss drug phentermine saw an end to one of the most successful weight loss drugs. Though the cause of the ban was the very effective side-effects, phentermine proved to be very effective for a large section of the people. However, one can resist thinking that maybe of all the phentermine victims there might be some who have gone for no prescription phentermine and bore the consequences.

Anonymous said...

Weight loss truths keeps you updated with latest information on weight loss tips, exercises, books and diets apart from enhancing your acumen with in-depth knowledge of traditional weight loss stuff and issues.For more information visit

Healthy Diet for Quick Weight Loss said...


I visited your blog through Google and found it to be informative and interesting. Really it's a great blog.

Everybody wants a quick weight loss miracle. We don't want to wait for good things to happen in our lives in our modern, instant pleasure society. The problem is, in our rush towards quick weight loss, we often forget about self awareness.

Here, Some Excellent Features that Prevent Quick Weight Loss:

1. Quick Weight Loss Tip - Losing Weight is an Equation

losing weight means you have to eat lesser calories than what your body needs. This translates to crushing lesser calories than your daily energy requirement.

2. Quick Weight Loss Tip – Eat More Meals and Don’t Skip them

Spread your meals from 3 big meals, breakfast, lunch and dinner into 5-6 smaller meals comprising the 3 main light meals and 2-3 other snacking time. This would distribute your calorie intake and reach a good balance.

3. Quick Weight Loss Tip 3 - Eat Green Vegetables

Stock up your fridge with lots of leafy green vegetables and fruits. Vegetables and fruits are rich sources of fiber and water and add weight and volume to our food. This makes our stomachs full while maintaining a lower calorie count since fruits and vegetables are inherently low in calories and fat content. They also pack our bodies with healthy nutrients making our diet a balanced one.

4. Quick Weight Loss Tip 4 – Sleep Well

Sleeping is a favorite quick weight loss tip since it is one of the most effortless. Do not understand the power of having enough sleep. Likewise, having sufficient sleep of at least 8 hours helps to bring a balance to the leptons level and aids weight loss.

Further, If you want to know more about Quick Weight Tips just log on to the below link:

Quick Weight Loss

Keep up the Great work!!!!!

Anonymous said...

If you have fallen prey to obesity and would like to trigger off weight loss as soon as possible, then you should opt for diet pills such as Phentermine and Adipex that are extremely popular for inducing rapid weight loss among people across the world. You will find the relevant details of weight loss pills at that inform you that Phentermine is to be taken only after procuring a Phentermine prescription and also in accordance with the instructions of the doctor. So, get hold of a Phentermine prescription, administer the drug properly and transform your weight loss dreams into reality.