Poor Inuits. Source
Here, I discuss eating for your activity levels, which is generally the first step in individualizing your eating plan. I could end this blog post by saying, "if you train hard and frequently, eat more; if you train like a wimp and less often, eat less". But then I would be doing you a disservice since there are additional details to an over-generalized statement like that. Of course, there rings some truth as well. If you tend to train more, like a competitive marathon runner or a competitive powerlifter, then you do need to eat more than someone who doesn't train that way. But when I say activity levels, I really mean the type of exercise you do and how often you do it determines the composition of your diet.
Put simply, the two athletes above should not eat the same way despite having high activity levels. Different activity types put different demands on energy substrate use, or what the body uses for energy. Goals also determine the composition of the diet. So the three things that determine how you structure your eating plan: 1) type of exercise; 2) frequency of exercise; 3) goals.
Overweight coach potato who wants to lose weight? Less carbs.
Endurance runner who wants to increase performance? More carbs.
General fitness guy/gal who wants to increase muscle mass and decrease fat but stay around the same weight (body recomposition)? Moderate carbs.
There is a large problem with making sweeping generalizations like this and that has to do with the individualization bit. Two people could be on the same diet and exercise regime and see different results. This can be explained by a variety of factors, but genetics, previous dieting history, and food intolerance are three of the most prevalent. But generally speaking (and for the sake of this post on activity) you really do not need to eat high amounts of carbohydrates unless you are involved in heavy and/or frequent training.
Before we get into the meat and potatoes, I am going to re-emphasize the three things I look at when structuring eating plans: type of exercise, frequency of exercise, and goals. Do not forget these.
All fruits, grains, legumes, and some vegetables contain carbs. Source
First, what are carbohydrates and how do they affect the body?
A carb (carbohydrate) one of the three main energy producing macronutrients--protein and fat the others. It is used preferably by the brain, provides 4 calories per gram, and ultimately gets broken down into three simple sugar molecules called glucose, maltose, and galactose. For our intents, glucose is what we want to focus on. Ingestion (or eating) of carbs increases the amount of sugar in the blood glucose (blood sugar), which prompts the pancreas (an organ) to release insulin, an extremely important but double-edged hormone. Insulin has a variety of functions and a couple of them are:
- Clears sugars from the blood by allowing them to enter fat, muscle, and liver tissue
- Acts as an anti-inflammatory agent
- Stops fat-burning and turns on building, or anabolic, processes
Insulin is so important that you cannot survive without it. To get an idea, Type 2 and type 1 diabetes are diseases where the cells of the body either do not respond to insulin or the pancreas does not produce enough insulin. In both cases, there is a problem with insulin. However, the double-edge is that too much insulin also causes problems. For us fitness folks who don't have diabetes, this applies because too much insulin stops fat-burning and turns on anabolic processes. One such building process is the storing of fats in fat and liver tissues leading to their subsequent enlargement.
The human body is a machine and each organ represents a piece of that machinery, a cog. Over time if you stress that cog enough (high carb diets stress the pancreas), you will exhaust it, causing it to fail. To put it rather simply, type 2 diabetes is generally caused by too much carbs (and low physical activity). Of course, we all break down eventually, no matter how healthy our diets are. But I am sure we all want to look good before getting recycled. I, for one, feel terrible recycling a nice looking wine bottle.
Now, the three main types of diets that manipulate carbs...
Low-carbohydrate Diets
Low-carbohydrate (LC) diets generally provide less than 20% of total calories through carbohydrates and are huge controversial topics. Talk to any person involved in nutrition about low-carbohydrate diets versus high-carbohydrate diets and it can start to resemble a religious battle quite fast. Despite how much people rage over which carbohydrate diet is better, there is a striking amount of research about LC diets. What most of the research says is that LC diets outperform conventional diets in the first 6-months to a statistical significant degree, but the results begin to diminish slowly afterward and eventually show no difference at one-year (1). Many of these studies were done on untrained and sometimes obese populations.
LC diets have also been shown to decrease symptoms of Metabolic Syndrome (decrease triglycerides, increase HDL, improve weight-loss) faster than conventional high-carb diets (2).
High-carbohydrate (HC) Diets
MyPlate, the government guidelines for nutrition, recommends nearly everyone to be on what I consider a high-carbohydrate diet. Their range is 45-65% of total calories. The most typical example of someone who should follow high-carbohydrate diets are endurance athletes. Other examples include athletes performing at high levels of various sports/events, like bodybuilders, sumo wrestlers, and track athletes and general fitness folks who are trying to build more mass.
Govt believes all meals should look like this. Source
The biggest drawback to a HC diet is that most of the energy comes from carbohydrates. Since carbohydrates provide your body with a quicker form of energy than fats and proteins, your body must then have an outlet for that energy, like putting fuel in a car. If you don't use that energy, or you keep putting more fuel in, you will experience some 'spill-over'. In scientific terms, this is called de novo lipogenesis (DNL). In other words, carbs will get converted to fat in the liver. However, the rate at which that happens is overblown by low-carb proponents and is actually quite low (4). The rate of DNL also depends on activity levels and genetics.
Moderate-carbohydrate (MC) Diets
If you do not fall into either of the two categories above, you will probably see the best results at the moderate range, which is usually 30-40%. Mark Sisson, author of the Primal Blueprint, and one of the biggest proponents of the 'primal' diet, created what's called a 'carbohydrate curve'. He believes that no one really involved in anything beyond general fitness should consume over 150g of carbohydrates per day. Paul and Shou-Ching Jaminent, authors of the Perfect Health Diet and also proponents of the primal movement, recommend the same thing. There are a few reasons why they recommend this yet their primary reason is that insulin can cause fat storage if too many carbs are eaten.
My take on the whole carbs = insulin = fat gain is that the amount of carbs you eat is context dependent, just like anything else. If you are a lot of carbs in the presence of pre-existing high carb intake combined with lack of activity, or an outlet for those carbs, then yes, you will gain some blubber. But if you are highly active and manipulate carbs appropriately, you will lose the flab. So though there are things I do not see eye-to-eye with both Mark and the Jaminets, I do generally agree with their stance on nutrition for general fitness folks looking to lose fat and improve body composition. Again, this does not apply to those performing at a high level or wanting to gain size.
The Perfect Health Diet apple. Source
How did we get to the conclusion of 150g of carbs? The human body only has a limited capacity to store carbohydrates. An average man can eat and store up to 15g per kilogram of bodyweight in carbs (storage form of carbs is called glycogen) (3). The key is, though, to never even get close to that point. Again, unless you are an endurance athlete or someone performing at a high level, you really do not need that many carbs stored. Additionally, depletion of glycogen may lead to better fat-loss via improved metabolic processes, such as fat-adaptation (body's ability to use more fat for energy rather than carbs) and by allowing you to be more liberal with carbs on days when you need them. Glycogen depletion itself is not a mode of fat-loss. In fact, glycogen depletion is what most people experience on their first couple days of an intense diet; in other words water loss.
Now I do recommend a moderate carbohydrate intake for most general fitness clients. If you resistance-train 3-4 days per week and your goals are to 'tone your arms' and 'lose some belly fat', you will probably follow a moderate carbohydrate diet and eat no more than 150g of carbohydrates per day (in the beginning). However, as you progress in your training, you will start incorporating re-feeds (more on that in later blog posts).
The Carb Curve. Source
References
1. Foster GD, Wyatt HR, Hill JO, et al. A Randomized Trial of a Low-Carbohydrate Diet for Obesity. N Engl J Med. 2003. 348:2082-2090.
2. Schugar RC, Crawford PA. Low-carbohydrate ketogenic diets, glucose homeostasis, and nonalcoholic fatty liver disease. Curr Opin Clin Nutr Metab Care. 2012 Jul;15(4):374-80
3. Acheson KJ, Schutz Y, Bessard T. Glycogen storage capacity and de novo lipogenesis during massive carbohydrate overfeeding in man. Am J Clin Nutr. 1988 Aug;48(2):240-7.
4. Schwarz JM, Neese RA, Turner S, et al. Short-term alterations in carbohydrate intake in humans. Striking effects on hepatic glucose production, de novo lipogenesis, lipolysis, and whole-body fuel selection. J Clin Invest. 1995 Dec;96(6): 2735-2743.
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