http://www.wannabebig.com/diet-and-nutrition/the-dirt-on-clean-eating/
Applying Moderation: The 10-20% Guideline
For those hoping that I’ll tell you to have fun eating whatever you want, you’re in luck. But, like everything in life, you’ll have to moderate your indulgence, and the 10-20% guideline is the best way I’ve found to do this. There currently is no compelling evidence suggesting that a diet whose calories are 80-90% from whole & minimally processed foods is not prudent enough for maximizing health, longevity, body composition, or training performance. As a matter of fact, research I just discussed points to the possibility that it’s more psychologically sound to allow a certain amount of flexibility for indulgences rather than none at all. And just to reiterate, processed does not always mean devoid of nutritional value. Whey and whey/casein blends are prime examples of nutritional powerhouses that happen to be removed from their original food matrix.
Use the 10-20% discretionary intake rule and enjoy life a bit.
The 10-20% guideline isn’t only something I’ve used successfully with clients; it’s also within the bounds of research. Aside from field observations, there are three lines of evidence that happen to concur with this guideline. I’ll start with the most liberal one and work my way down. The current Dietary Reference Intakes report by Food & Nutrition Board of the Institute of Medicine lists the upper limit of added sugars as 25% of total calories [24]. Similarly, an exhaustive literature review by Gibson and colleagues found that 20% of total calories from added sugars is roughly the maximum amount that won’t adversely dilute the diet’s concentration of essential micronutrition [25]. Keep in mind that both of these figures are in reference to refined, extrinsic sugars, not naturally occurring sugars within whole foods like fruit or milk. Finally, the USDA has attempted to teach moderation with their concept of the discretionary calorie allotment, defined as follows [26]:
“…the difference between total energy requirements and the energy consumed to meet recommended nutrient intakes.”
Basically, discretionary calories comprise the margin of leftover calories that can be used flexibly once essential nutrient needs are met. Coincidentally, the USDA’s discretionary calorie allotment averages at approximately 10-20% of total calories [27]. Take note that discretionary calories are not just confined to added sugars. Any food or beverage is fair game. The USDA’s system is still far from perfect, since it includes naturally-occurring fats in certain foods as part of the discretionary calorie allotment. This is an obvious holdover from the fat-phobic era that the USDA clings to, despite substantial evidence to the contrary [28].
It’s important to keep in mind that protein and fat intake should not be compromised for the sake of fitting discretionary foods into the diet. In other words, make sure discretionary intake doesn’t consistently displace essential micro- & macronutrient needs, and this includes minimum daily protein and fat targets, which vary individually. This may be tough to accept, but alcohol is not an essential nutrient. Its risks can swiftly trump its benefits if it’s consumed in excess, so it falls into the discretionary category.
10% Versus 20%
Another legitimate question is why I’ve listed the discretionary range as 10-20% rather than just listing it as a maximum of 20%. This is because energy balance matters. In bulking scenarios, maintaining a 20% limit could potentially pose health risks that are already elevated by the process of weight gain, which in some cases involves a certain amount of fat gain. Conversely, weight loss tends to be an inherently cardioprotective process, independent of diet composition [29]. So, the 20% limit is more appropriate for those either losing or maintaining weight. Those who are gaining weight but want to play it safe should hover towards the lower & middle of the range (10-15%). Another factor that can influence the upper safe threshold is physical activity level. I’ll quote Johnson & Murray in a recent review [30]:
“Obesity and metabolic syndrome are rare among athletes, even though dietary fructose intake is often high, underscoring the robust protective role of regular exercise.”
In the above quote, you can substitute any controversial food or nutrient in place of the word fructose, and the same principle would apply. A greater range of dietary flexibility is one of the luxuries of regular training. Sedentary individuals do not have the same level of safeguarding from the potentially adverse effects of a higher proportion of indulgence foods. And just in case it wasn’t made clear enough, 10-20% indicates the maximum, not minimum discretionary allotment. If someone strives to consume 0% of calories from any food that’s been processed or refined from its original state, then that’s perfectly fine – as long as this is the person’s genuine preference, and not a painful battle of will. I’d also like to make it clear that there is still plenty of grey area in the study of dietary effects on health. As such, the nature and extent of the miscellaneous or rule-free food allotment is a delicate judgment call. In this case, it’s wise to keep scientific research at the head of the judging panel, but don’t ignore personal experience & individual feedback.
Final Note: Linear Versus Nonlinear Distribution
A legitimate question is, what’s the best way to distribute discretionary calories? Should they be confined to a daily limit, or can it be a weekly limit? The best answer is to let personal preference decide. If we use a 2000 kcal diet as an example, a flat/linear approach would mean that 200-400 kcal per day can come from whatever you want, while meeting essential needs otherwise in the diet. Weekly, this translates to 1400-2800 kcal, depending on the factors I previously discussed. One nonlinear option would be to break the weekly allotment in half, where 2 days per week you indulge in 700-1400 kcal of whatever you want, keeping the remaining 5 days relatively Spartan. Again, there is no universally superior method of distributing the discretionary allotment. The same principle applies to the choice of foods to fulfill it. Honoring personal preference is one of the most powerful yet underrated tactics for achieving optimal health and body composition. And that’s the nitty-gritty as I see it.
