|You might be able to buy a bowl like this here.|
Now let me be clear right out of the gate, the study I’m about to discuss found that alternate day fasting led to just as much weight loss as tracking calories. But there was one difference.
The study, a randomized, controlled, year long affair assigned 222 patients to either:
- Alternate day fasting
- Daily calorie restriction
For the first 3 months, both the fasting group and the calorie restriction group received all their meals from the study coordinators. For the next 3 months, both groups were encouraged to reduce their energy intake by 25% per day. The fasters were told to consume 25% of their baseline daily calories as a lunch (between 12 pm and 2 pm) on fast days and 125% of their baseline daily calories split between 3 meals on alternating feast days. The calorie restrictors were told to consume 75% of their baseline daily calories split between 3 meals. For the last six months, following the calculation of total daily energy expenditure (by way of doubly labeled water), participants were instructed to maintain their body weights. Fasters were advised to consume 50% of their calculated energy needs at lunch on fast days, and 150% of their energy needs split between 3 meals on alternating feast days. Restrictors were told to stop restricting and instead to consume 100% of their energy needs split between 3 meals.
Throughout it all, both intervention groups received support and counselling from RDs.
The study’s primary outcome was weight loss. Physical activity was controlled for and calculated by two 1 week periods of accelerometer use. Dietary adherence was monitored by way of food recall.
Secondary outcomes were blood pressure, heart rate, total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, fasting glucose, fasting insulin, C-reactive protein, and homocysteine concentrations.
Weight loss wise, as you can see from the graph, at virtually no point in time during the year long study was there was a difference found between fasters and restrictors (triangles and squares).
There were also no statistically significant changes found to body composition between the groups.
At 12 months, there were also no differences to be found in any of the secondary outcomes or measures.
In fact the only difference the researchers found was to adherence.
More people dropped out of the fasting intervention (38%) than of the restricting intervention (29%).
I’m not sure how surprising that finding is, as fasting may be challenging for many with respect to lifestyle including to family meal times, socializing with friends, and eating with coworkers.
Or maybe it leads people to be more hangry?
All this to say, if you enjoy fasting as a lifestyle, go for it. But no, it doesn’t appear, at least not from this study, that fasting has any magical properties.