Intermittent Fasting has many beneficial health benefits, but if you're looking for weight loss, it seems (at least in rats) you had better combine it with calorie reduction. In this landmark study scientists note:
"By the end of this study, male C57BL 6 mice subjected to IF [intermittent Fast]
were consuming essentially the same amount of food in a 48-h
period as did those fed AL [Ad Libitum]. On the days they had access to food,
the IF mice ate roughly twice as much as did mice fed AL (Fig.
1a). Mice on the LDF [Limited Daily Feeding] regimen consumed 40% less food as
provided: this was reflected in their body weights, which were
49% lower than those of the AL-fed group. In contrast, at the
end of the study the body weights of mice maintained on the IF
diet or PF on a daily basis were only slightly below those of the
But of course most of us practicing intermittent fasting, are not eating double the amount of calories to make up for it.
In fact, the IF that I practice might resemble more closely slight calorie restriction plus a small fasting period. I suppose I am hoping to get at least a small dose of the helpful benefits of each method. Besides I could not imagine fasting 36 hours every other day. That would be torture!
Alas, there are very similar benefits for insulin sensitivity betweem IF and Calorie Restriction:
"A prominent physiological change that
occurs in mammals maintained on reduced-calorie diets is
increased insulin sensitivity, which often is reflected in decreased fasting plasma levels of glucose and insulin (17). Fasting
serum concentrations of glucose and insulin in mice fed AL in
the current study averaged 150 mg dl and 3,400 pg ml, respectively (Fig. 2 a and b). The concentrations of glucose and insulin
were decreased significantly, to similar amounts, in mice maintained on either LDF or IF regimens with glucose and insulin
concentrations dropping to 100 mg dl and 700–1,100 pg ml,
respectively (Fig. 2). That similar changes are seen in IF and LDF
groups in the current study suggests that despite an overall
calorie intake similar to mice fed AL, IF has similar effects on
circulating glucose and insulin levels."
So that's good news for Rats on IF or CR!
Calorie Restriction VS Intermittent Fasting Both Healthy, but...