|This is how the "buffered" alternate day fast works: You eat 1/4 of the White Choc Banana Cream Pie on your fasting day and a whole pie on the next one - well, not really, but the ratios would be right ;-)|
A brief warning with respect to the data in figure 1: I know that a couple of you are too lazy to actually read the article and do headline + figure hopping. If you intend to to that, please keep in mind that the data in figure 1 is from another recent study, I used to illustrate the negative effects of "real" alternate day fasting.
Not all alternate day fasting is created equal
For the course of this 12-week, randomized, controlled, parallel-arm feeding trial the participants, 61 women and only 3 men aged 25 to 65 years, overweight / obese (BMI 30-39.9kg/m²) and weight stable for at least 3 months were randomized to one of the four study arms (unfortunately the data does not allow for any conclusions, whether the men and women reacted differently to the intervention or "real" alternate day fasting the data from the rodent study I discuss in the interlude surrounding figure 1 shows that this is the case, though):
- control group (C): sedentary, no diet
- exercise group (E): 25, 30, 35, 40min at intensities of 60, 65, 70, 56% of the calculated HRmax (intensity and duration were increased in week 4, 7 and 10)
- alternate day fasting group (ADF): after 4-week controlled feeding period the study concluded with an 8-week self-selected feeding period.
As long as study subjects just have to eat what scientists serve them, every diet works. When they are however told to eat a high protein diet, for example, even the reported nutrient intake diverges massively from what the scientists had in mind, when they devised the protocol - you don't believe me? Well, then read for yourself, "What Really Happens, When Science Meets the Real World"
increasing fruit and vegetable intake." (Bhutani. 2013)
- combination group (ADF + E): combination of alternate day fasting and exercise protocol
|Table 1: Nutrient composition of the fast day diet provided to the combination and ADF groups (Bhutani. 2013)|
Let's briefly take a look why "real" alternate day fasting may not be a good idea
As you can see the effect of the alternate day fasting regimen in the Kumar study, in the course of which the rodents simply did not receive any food for a whole day, had profound negative effects on the hypothalamo-gypophysial-gonadal axis - especially in the female rodents.
|Figure 1: Effects of every-other day fasting vs.ad libitum feeding on ovarian weight, estradiol, lutenizing hormone, leptin, and testosterone in female and male rodents (Kumar. 2013)|
Now why didn't these adverse events occur in the study at hand?
Actually I am only assuming that there were not similar negative effects in the study at hand. After all, we don't have the respective hormonal and even in the rodents it took it's time (2 cycles) until the females were totally infertile. Changes like these would thus probably have gone unrecognized. I do however suspect that the major factors contributing to the overall hormonal decline in the rodent study were the extendended time-span without food and the overall caloric deficit, which is usually ~30-40% of the habitual intake in rodents on alternate day fasting regimen, as they do not compensate for the fasting day on the subsequent day.
|Figure 2: Changes in body composition in the combined, ADF, exercise and control groups (Bhutani. 2013)|
|Figure 3: Changes in lipid profile (left) and glucose metabolism in the combined, ADF, exercise and control groups (Bhutani. 2013)|
|Image 2: Ramadan fasting can serve as a relatively well studied "model" of intermittent fasting. With the additional restriction of water intake and the common practice of rising early to have breakfast there are yet non-negligible differences. You can find more information about the strengths and limitations of this model in Part 2 and Part 3 of the IF series.|
"the combinationof ADF plus exercise decreased LDL cholesterol (12% from baseline) while increasing HDL cholesterol (18% from baseline); a change that was not noted for any other intervention. The combination group also experienced an increase in LDL particle size, and a reduction in the proportion of small LDL and HDL particles." (Bhutani. 2013)Only later in the discussion of their results do they mention that those "CHD risk indicators" improved to the same extend in the ADF only group - with even more significant changes in the particle profile.
|Learn why breakfast is probably not the "most", but rather the least "important meal of the day" (read more).|
Keeping all that in mind I am still not convinced that a regular intermittent fasting routine (16-18h fasting window on every day; learn more about intermittent fasting here at the SuppVersity) and a combined aerobic + strength training regimen would not have yielded even superior results. The average physical culturist probably will be better of with this by now almost "classic" diet routine.
- Bhutani S, Klempel MC, Kroeger CM, Trepanowski JF, Varady KA. Alternate day fasting and endurance exercise combine to reduce body weight and favorably alter plasma lipids in obese humans. Obesity (Silver Spring). 2013 Feb 14.
- Kumar S, Kaur G. Intermittent Fasting Dietary Restriction Regimen Negatively Influences Reproduction in Young Rats: A Study of Hypothalamo-Hypophysial-Gonadal Axis. PLoS ONE. 2013; 8(1): e52416.