"Special K Challenge" - What does it challenge? Weight loss or yo-yo-effect?
In the respective 14-day intervention trial 24 subjects (12 men and 12 women) with a mean age of 34.7 years and a pretty chubby physique (BMI 28.6 kg/m², but body fat 28.8% and 40.7% for men and women, respectively) had to follow the "Special K Challenge" (official website), the central idea of which is that you are going to lose weight and get healthier if you replace two of your regular meals by a predefined amount of yummy (and nutritious *rofl*) expensive cornflakes, ah... I mean "Special K"...
|Figure 1: Macronutrient composition of the 174kcal Special K + skim milk "meal replacement" and the Special K Snack Bars (83kcal) and Mini Breaks (99kcal) the participants consumed during the 14-day challenge and the consequent reductions in protein and fat intake relative to baseline (data calculated based on Shaw. 2011)|
- Control phase: Do what you usually do and eat what you usually eat for two weeks, log all your foods and get back to the lab to get another body weight, body water, body fat, lean body mass (the latter two via DXA scans), waist and hip circumference measurement taken.
- Special K Challenge: Keep doing what you usually do, keep eating what you usually eat, but replace 2 of your main dishes with Special K + semi skimmed milk and eat fruit and/or Special K Mini Breaks or Special K Snack Bars between meals (cf. figure 1), log everything you eat and return your hopefully lighter self as well as the logs to the lab in another two weeks.
"I want my pizza back!"- and "I better completely stop eating to maximize weight loss"-effect
What is similarly unsurprising, is that the overall calorie intake is reduced (avg. energy deficit: 673kcal/day) by a "challenge" , in the course of which two of the main meals (of which most people obviously consume only three) are replaced with a 174kcal "meal replacement" in form of yummy cornflakes with watery skim milk (aside from the "bah, I want my pizza"-effect, I am thinking about the "hyperpalatability hypothesis" here, as well; cf. Guyenet. 2011). That it is so profoundly reduced that at least one male subject had a caloric deficit of 1555kcal per day (!), however, clearly suggests that the end-result of this type of "diet" (or shall we call it a hunger-strike?) is not going to work. It is thus all the more surprising, that, according to the conclusion of the abstract, ...
The results of the present study demonstrate that the Special K Challenge was effective in reducing total energy intake and resulted in a positive, health-related change in body composition. The reduction in total body mass, regional fat mass and waist circumference may act as an effective motivator to long term body mass reduction.Certainly worth taking a closer look at the data, right? Well, for the first point, i.e. "effective in reducing total energy intake", we already know that this is true. "Effective", by the way, is effectively understated. Now, what about the "positive, health-related change in body composition"? What would that imply? A reduction in body fat and an increase in lean mass, right! And what have we got?
|Figure 2: Lean mass and fat mass of 24 overweight men and women before 2-week accommodation phase (pre) and before (basal) and after (Special K) 14-day "Special K Challenge" (data adapted from Shaw. 2011)|
"But it does work! So what do you want?"
Even if you are not effected by it yourself, I bet that everyone of you knows someone who has maybe not even gained weight, but has become fatter and fatter with every diet he (or presumably "she") has "done". This study on the "Special K Challenge" shows you exactly what went wrong for him/her/them:
|Image 2: Although common wisdom would say so, eating salad is no alternative either... when I come to think about it, it may be an alternative to eating toilette paper, but that won't help with fat (not just weight!) loss either.|
- believing in the existence of a "quick fix" and/or "convenient solution" that will work in 1-2 months, let alone weeks and thusly
- going on a diet instead of changing your diet as part of changing your lifestyle
- not meeting your minimal energy requirements / starving yourself
- not having enough protein and fat with EVERY meal
- snacking, in general, and on processed foods, in particular
- no exercise (in this case), or tons of endurance exercise to exercise your "cheats" away
- using the scale as a measure of success