Two of the latest buzz-words on the scene in the nutrition and diet media which nowadays refers to the countless facebook posts that clog up your news feed, are “ Intermittent Fasting ”.
I know what you’re thinking, “Fasting? Really? This is something nutrition and diet experts have said is the absolute WORST thing you could do.” Well, what if we were wrong? Furthermore if you’re thinking “I cannot go without a meal for 6 hours or more” then you’re also wrong. Most of us do it every single day. We just call it sleeping.
There are numerous anecdotal stories circulating regarding the benefits of intermittent fasting for weight loss, diabetes control, decreased cardiovascular disease risk, cancer-fighting and even anti-aging! In this article I wanted to examine the claim regarding weight loss and determine if there is scientific evidence to come to its defense.
Claim: Intermittent Fasting For Fast Weight Loss
In the scientific community, new evidence is found on a daily basis, and intermittent fasting is certainly an up and coming topic. Here is a summary of the research available currently:
- An intermittent fasting or temporary caloric restriction regimen can result in a weight loss of up to 5% in 6 days [1, 2, 3, 4].
- Post-fast, average spontaneous energy intake (how much food you want to eat) doesn’t increase as dramatically as expected. On average the spontaneous energy intake only increased by 20% at the first meal post fast, where people tend to choose higher fat, energy-dense meals. Following this first high-energy meal, spontaneous energy intake returns to normal. Simplified, this means that if your first meal after the fast ends is high in energy (with good fats and adequate protein) then your hunger level will not be higher than normal. So to maintain your weight losses, the fast should be followed by the introduction of a real-food based, healthy-fat-containing diet.
- Individuals who undertook complete fasting for at least a 24hour period found that they were able to maintain weight loss up to 1 year after the study was conducted . The study participants reported however that they periodically used the fasting technique to maintain their weight as desired. They also indicated that they were surprised by their ability to complete a total fast. This ties in with one of my take-home points so stay tuned for those below!
- During the fasting period, hunger levels definitely increase at least initially [2, 3, 4]. This means that more dedication and motivation will be needed in the beginning. As time goes on, however, the literature does indicate that hunger may go away as Wadden et al report “less food eaten results in less hunger” .
- Fatigue is a real side-effect, also at least initially [6, 7,8]. This fatigue may lead to decreased productivity at work and also decreased energy expenditure because of a lowered desire for exercise.
- Actual composition of the weight loss may be more water, glycogen stores and protein stores instead of actual fat. Losses of lean protein account for the majority of the body weight decreases during total starvation, with body water losses being a close second [9, 10]. Several studies have shown that low-carbohydrate diets can lead to greater weight loss, compared with diets with the same number of calories but higher in carbohydrates . Of the few studies that have looked at the composition of weight loss on low carbohydrate diets, a trend has been shown for favouring fat loss and preserving (or even increasing) lean muscle mass . Perhaps this is something to consider as an alternate weight-loss solution?
Some quick take home-messages:
- A Trial Fast may be of benefit for practicing how to manage hunger, as well as learning how to distinguish between psychological hunger and physical hunger. Basically, if you need to abstain from eating that unhealthy food just because it’s the only thing available – you can!
- More Regular Fasting may make it easier to maintain a lower body weight and fat percentage when compared to conventional diets.
- More Regular Fasting may not objectively be better for the initial process of losing body fat when compared to alternate diets e.g. a lower carbohydrate diet. Lean muscle mass may actually suffer in prolonged fasting.
- Intermittent Fasting can work but may not be for everyone, and more importantly may not need to be. It is one approach among quite a few very effective ones.
- Intermittent Fasting is most especially NOT a way to indulge bad eating habits and avoid the consequences. This is probably the most important take-home message!
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