Based on my experience with intermittent fasting, I have discovered a few characteristics of a person who might really thrive on intermittent fasting. Check out the list below to see if you might be one of them!

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Likely Good Candidates:

  • Absent or minimal hunger cues or doesn’t mind being hungry – I often hear “I often forget to eat” or “I could go all day without eating”
  • Not usually hungry in the morning/prefers to skip breakfast
  • Dislikes the structure of tracking calories daily
  • Prefers limiting intakes significantly sometimes and not regulating at all at other times
  • Schedule that allows eating at “unconventional” times (for 16:8 protocol)
  • Goals might include: weight loss, decreased inflammation, reduced risk for chronic diseases like diabetes, heart disease, Alzheimer’s

 

Likely Not Good Candidates:

  • Frequent hunger (every 3-4 hours or less)
  • Regular breakfast eater
  • Prefers more structured eating regimen
  • Prefers moderating intakes a little each day to an “all or nothing” mindset
  • Goals might include: weight loss, muscle gain, reduced risk for chronic diseases like diabetes, heart disease, Alzheimer’s

If you want to learn more about creating a personalized plan to meet your goals and fit your lifestyle, visit my practice website and set up an appointment!


I’ve been busy researching, reading, and compiling more information from scientific studies done on intermittent fasting and its potential benefits. This is part two, but you can go here to read about more research on fasting or here if you’re not sure what intermittent fasting is all about.

Can intermittent fasting…

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…improve blood sugars and prevent/manage diabetes?

  • Animals that ate intermittently exhibited resistance to diabetes and improved blood glucose and insulin sensitivity, even if they did not achieve caloric restriction (Anson et al 2003Duan et al 2003)
  • Animals on daily caloric restriction have lower fasting blood glucose, fasting insulin, reduced inflammatory markers, and improved insulin sensitivity (Lane, Ingram, Roth 1999Imai 2010Hursting et al 2003Lane et al 1995; Wang et al 2007Bonkowski et al 2006Okauchi et al 1995; Walford et al 1999; Walford et al 2002; Wang et al 2007Kalani et al 2006)
  • Human results on intermittent fasting are mixed:
    • One study found no change in glucose but lower fasting insulin after 22 days of intermittent fasting (Hielbronn et al Jan 2005).
    • One study found that, while fasting, subjects with diabetes had higher blood sugar levels (Saada et al 2010).
    • Another found that after 22 days of intermittent fasting, women’s bodies showed more difficulty clearing blood glucose but that there was no difference in men. Men also had a decreased insulin response, but women didn’t. (Hielbronn et al Mar 2005).
    • Another study found no change in glucose or insulin in men after 14 days of intermittent fasting (Halberg et al 2005).
    • Two studies found that in humans, insulin sensitivity is more improved with fasting than with caloric restriction (Varady & Hellerstein 2007; Harvie et al 2010)
  • Humans on caloric restriction showed lower fasting insulin levels, improved insulin sensitivity, and lower blood glucose. (Hielbronn et al 2006; Weiss et al 2006; Fontana et al 2004).
  • The boiled-down verdict: Animals show improvements in blood glucose, insulin sensitivity, and resistance to diabetes with both intermittent fasting (without caloric restriction) as well as caloric restriction (without intermittent fasting). In humans, research on intermittent fasting and blood sugars delivers mixed messages, which probably means there are other factors involved that we don’t understand yet. There might be a gender difference in the blood glucose response to intermittent fasting. Several studies showed that daily caloric restriction can improve fasting insulin levels, insulin sensitivity, and blood glucose in humans.

 

…treat asthma?

  • In one study, intermittent fasting reduced airway resistance, reduced inflammation, and improved the medicinal effects of albuterol in patients with asthma. (Johnson et al 2007)
  • The boiled-down verdict: We need more research, but intermittent fasting may have some promising benefits for those with asthma.

 

…decrease risk of heart disease?

 

…slow cancer?

  • Animals that eat intermittently exhibit slowed tumor growth, improved the effectiveness of chemotherapy, and reduced side effects of chemotherapy (Berrigan et al 2002;Lee at al 2012).
  • In mice, intermittent fasting without caloric restriction reduced the occurrence and growth of lymphoma (Descamps et al 2005).
  • Several studies show that animals with tumors had slower tumor growth and lived longer when calorically restricted with adequate protein, vitamin, and mineral intakes (Weindruch et al 1986Pashko & Shwartz 1996Pugh et al 1999; Imai 2010Hursting et al 2003); however, one study showed mice had no slowing of tumor growth when on caloric restriction (Keenan et al 1997).
  • Reviews of animal research conclude that the cancer prevention/slowing benefits are similar between intermittent fasting and calorie restriction (Varady & Hellerstein 2007).
  • The boiled-down verdict: Research on the benefits of caloric restriction for cancer is mixed. Intermittent fasting may slow tumor growth and improve the effects of cancer treatment in animals. We need more research to know how these effects may transfer over to humans.

And just like that, 3 weeks of intermittent fasting is over. In the last week, I changed the structure of my intermittent fasting a little bit. I followed a pre-made intermittent fasting plan that had a 12 pm – 8 pm eating window and planned meals and workouts. The workouts were more targeted for fat loss and not for muscle building (which were my goals with my previous workouts). Changing the workouts allowed me to aim for slightly lower calorie goals since losing fat requires fewer calories than gaining muscle.

Let’s review the entire three weeks, shall we?

 

How it Went:

Unfortunately, I did not enjoy the experience of intermittent fasting. I’m a lifelong breakfast eater – can’t even remember ever skipping one – so not eating until 10 am or noon (depending on my window) was pretty miserable. I was super hungry, weak-feeling, and tired in the mornings, and I noticed that I was more tired as the three weeks went on. I’m not sure if this was related to the eating schedule itself or not, because I also realized that throughout the three weeks I ate fewer vegetables than normal. This was sort of an interesting “side effect” of the eating schedule. Because I was trying to fit all my macros in a small window (and was full throughout most of that window), I ate vegetables less often because I didn’t have space for them! For the most part, vegetables have very few macronutrients (carbs, protein, or fat) and a lot of micronutrients (vitamins and minerals). I often recommend clients increase vegetable intake to help with fullness without adding a lot of calories or macronutrients – the opposite happened here! I was so full throughout the eating window that I strayed away from veggies and towards things that were going to help me meet my macro goals. As a result, my vitamin and mineral intake was much lower than normal, and could definitely have caused my tiredness.

One positive change I noticed is that I liked not eating later in the evening. There are reasons to avoid eating close to bedtime, and having a set time that my eating window “closed” prevented me from going to bed on a stomach full of energy I didn’t need, as well as habitual (not hunger-driven) nighttime snacking and desserts. I usually felt pretty good in the evenings.

As a side note, I love to cook and eat food in general, but I tended not to look forward as much to eating because I was either hungry and waiting to eat or full and had to eat anyway. Eating this way was much less enjoyable and satisfying for me than intuitive eating on a schedule that works well for my body.

 

What I Learned:

While reviewing the research on intermittent fasting this week, I discovered that researchers have almost exclusively studied alternate day or 5:2 fasting protocols rather than the 16:8 protocol that I followed. If you’re confused about what those protocols mean, check out this post. I wish I would have read through more research before I started, because I might have followed those protocols instead just to match the research.

From a dietitian’s perspective, I learned that there are certain people with certain goals who are good candidates for intermittent fasting and for whom it might work wonderfully. In fact, throughout my time on this diet I met several people (or found out about people I already knew) who use intermittent fasting to regulate their intakes and benefit their health. I plan to summarize characteristics of those folks in an upcoming post! The research is clear that intermittent fasting is one way to achieve quite a few health goals (though there are other ways!). In my practice, I will keep intermittent fasting as another option in my dietitian “tool belt” to help create plans that best match each client’s personality, lifestyle, and goals.

 

How I did and What Changed:

Overall in 3 weeks, I lost 3.6 lbs, 1.75″ from my waist, 1″ from my thighs and 1.6% body fat. Not too shabby!

 

  Goal Week #1 Week #2
# of days 16-hour fast was achieved 7 6 7
Average daily protein intake 90 grams 85.4 grams 82.2 grams
Average daily carb intake 225 grams 209 grams 205 grams
Average daily fat intake 60 grams 73.2 grams 64 grams
Weight change   0 lbs -1.2 lbs
Body fat % change   -.5% -.5%
Waist measurement change   -1″ +.75″
Hip measurement change   0” 0”
Thigh measurement change   -1″ +.5″

 

The third week is on its own because when I changed my workouts, my calorie and macro needs changed. The meal plan I used that week must have been built on different macro targets than I had set, because I ended up higher on fat and lower on carbs and protein in general. I did the best at hitting my macro goals in the second half of week two, when I broke my needs down into a schedule with macro goals at each meal. It’s important to note here, though, that in the research studies, they often did not track macros or make sure that subjects were meeting their calculated macro needs. In fact, in many of the human studies, the subjects often did not end up meeting their calculated calorie needs.

  Goal Week #3
# of days 16-hour fast was achieved 7 6
Average daily protein intake 80 grams 66 grams
Average daily carb intake 200 grams 159 grams
Average daily fat intake 53 grams 71 grams
Weight change   -2.4 lbs
Body fat % change   -.6%
Waist measurement change   -1.5″
Hip measurement change   0”
Thigh measurement change   -.5″