The Paleo diet has several things in common with traditional bodybuilding cuisine. One commonality is that both communities often shun wheat products like bread. Bodybuilders classify bread as a “dirty” food, as opposed to “clean” foods like chicken breast. The Paleo diet shuns wheat because of the way grains affect health.
Is this all dogma and fear mongering? Or is there scientific merit to the avoidance of bread? Since the health effects of grains, gluten and bread have been discussed several times over in the Paleo community, we’ll focus here on the effects of grains on your body composition. How do grains affect your ability to gain muscle and lose fat?
Before reviewing the effects of grains on your gains, let’s first discuss terminology so that we’re actually talking about the same things.
There are 2 main groups of food grains: cereals and legumes.
- Cereals are a form of grass. They include wheat, rice, maize (= corn), barley and oats.
- Legumes include beans, lentils, peas and peanuts. So peanuts are technically not a type of nut, though nutritionally there is little difference.
The problem with grains for your gains
Many plants have evolved defense mechanisms to protect their seeds from being eaten by animals. One of these mechanisms is the production of anti-nutrients that make the seed’s nutrients impossible or uncomfortable to digest by animals. Anti-nutrients occur in many foods, but grains have a particularly high amount of them.
Some of these anti-nutrients actually have positive health effects in humans, like preventing inflammation from high iron intakes. Altogether, though, it’s safe to say they are bad for people looking to affect physique.
For one, anti-nutrients greatly reduce the digestibility of minerals like magnesium and iron. Ironically, grains are often advertised for their high mineral contents, but mineral absorption is exceedingly poor compared to animal foods. On a calorie equated basis, grains aren’t very nutritious in comparison to most vegetables or organ meat to begin with. For example, only 13% of the magnesium in bread containing the anti-nutrient phytic acid is absorbed by the body. The results of insufficient body magnesium include insulin resistance, low testosterone, bone loss, stress hypersensitivity, high blood pressure and disturbed neuromuscular functioning. Getting enough magnesium can thus increase your testosterone, strength and endurance level. Iron uptake from bread can be as low as 3.8%. Iron deficiency impairs oxygen transport and thereby your endurance capacity and your resistance to fatigue; it has also been found to impair strength.
Perhaps more importantly for your physique, phytic acid also binds to protein, the crucial building block of your muscles. Several anti-nutrients inhibit trypsin and pepsin, enzymes that your body needs to digest protein. When your body can’t absorb the protein from your food, it cannot use it to build muscle tissue. Muscle growth is the result of positive protein balance: greater levels of muscle protein synthesis than protein breakdown.
Unfortunately, there is very little research on the effect of anti-nutrients on protein balance in humans. In animals, the effects are severe: anti-nutrients can reduce protein digestibility to less than half. In humans ,we know that Mexican diets with relatively high amounts of anti-nutrients reduced protein digestibility by 23%. Nitrogen balance, a scientific measure of protein balance, decreased by several fold, as did the digestibility of minerals.
It has also become a ‘fun fact’ in evidence-based fitness circles that brown rice consumption results in significantly lower nitrogen balance than white rice. This fact actually isn’t fun at all, because this effect is in large part due to the anti-nutrients in whole rice. These anti-nutrients mostly reside in the bran, so white rice does not have many anti-nutrients left: they are removed along with most of the nutrients.
Rice contains far fewer anti-nutrients than most other grains. Remember phytic acid, the anti-nutrient that makes protein indigestible? Rice typically contains less than a third of the phytic acid that wheat does.
So, wheat is likely far more detrimental to your protein balance than rice, especially white rice. This may explain why many bodybuilders see white rice as a ‘clean food’, whereas wheat products rarely appear in the diet.
Before abolishing all grains from your diet to protect your gains, remember that the human gut can produce an enzyme that breaks down phytic acid, so you may not have to completely avoid it in your diet.
Moreover, you can probably compensate for anti-nutrients by simply eating more nutrients.
In my review of the optimal protein intake for bodybuilders, I noted that protein quality did not seem to affect how much protein you need in practice. However, this was largely based on strength trainee diets, which tend to have a complete source of protein with every meal (a food containing all amino acids, like meat, poultry or fish). In contrast, a vegetarian diet is associated with lower muscle mass than an omnivorous diet with the same protein intake. So, a purely plant based diet loaded with anti-nutrients is likely no bueno for your muscles.
And there’s a caveat: anti-nutrients don’t just affect the digestibility of the protein you eat, they also affect the protein already in your body. During digestion, a portion of the nitrogen and amino acids in your digestive tract originate from your own body’s pool of amino acids. Normally, these amino acids are reabsorbed into the body, but anti-nutrients can inhibit this. As a result, amino acids are lost from your body. We currently only have relevant data on this in animals, so it remains speculative to what degree you can compensate for anti-nutrients by simply consuming more protein.
Fortunately, our ancestors were aware of the problems with grains that modern humans seem to have forgotten, so they came up with ingenious cooking methods to reduce the anti-nutrient content of grains, namely fermentation, sprouting and soaking. Ezekiel and sourdough bread are some of the last remaining commercially available traditional grain products, but you can find many more in Paleo communities. Compared to the bread you find in today’s supermarkets, sourdough bread often has better mineral bioavailability, a lower glycemic index, higher anti-oxidant activity and better protein digestibility. Put simply, it’s more nutritious…and more biceps friendly. Even people with Celiac disease can generally eat sourdough bread without issues. You could thus consider traditionally prepared grains “Paleo-lite.”
Wheat belly: does wheat hinder fat loss?
Melanson et al. (2006) compared the effectiveness of a weight loss diet in groups with or without whole-grain cereal in their diet. Both groups were put on an exercise program with cardio and stretching. The macros were supposed to be the same between groups, but the whole-grain group ended up consuming more fiber. This likely resulted in an unintentional reduction of energy intake compared to the diet without grains, though the between group difference did not reach statistical significance. Even with a greater energy deficit and fiber intake, the whole-grain group didn’t lose more weight during the 24-week study. In fact, weight loss slightly favored the no-grain group at both measurement points, but the results didn’t reach statistical significance.
Rave et al. (2007) compared the effectiveness of a weight loss diet based on Slim Fast, a sugary drink with supplemental fiber, against Cargill’s Balantose supplement: “a starch-reduced whole grain derived from double fermented wheat.” The diets had the same amount of calories, but there is no mention of the macros. The researchers did report the macros of the supplements: the grain supplement contained twice as much protein as the Slim Fast. In spite of this, there was no difference in weight loss or change in waist-to-hip ratio between groups. Yet again, the no-grain group lost a non-significant 28% more weight. Although that could have simply been because a common side-effect in the grain group was constipation. It’s always difficult to distinguish between whether someone’s “wheat belly” is the result of constipation and bloating or actual fat mass.
Cargill sponsored the study and one of the researchers worked for Cargill. This study reads an awful lot like the researchers didn’t find what they were hoping for and tried to make the best of it. They did manage to work their statistical magic on the insulin resistance data (by using the lower weight loss in the grain group to correct for the non-significant between-group difference and push the p-value just to 0.05) so that they could conclude grains are good for diabetics. I guess that will be better received than “Even with the added protein, this crap may be even worse than Slim Fast.”
Just like in the above 2 studies, in most controlled experiments, a whole grain diet is no more effective for fat loss than a processed grain diet [2, 3].
As such, it seems that whole grains may indeed provide a slight disadvantage to fat loss, enough to cancel out the benefits of the extra fiber and protein. Any small metabolic effect is likely related to the inflammatory effect of wheat on the digestive system, which can significantly impact energy expenditure, energy loss in stool, and nutrient partitioning (where your body stores nutrients) .
Thermodynamics and energy balance still apply, however, so it’s not like you can’t lose fat when you’re eating grains or as if grains automatically result in fat gain.
While scientific research is lacking, traditional bodybuilding and Paleo wisdom seem to have merit. Without soaking, fermenting or sprouting of the grains, strength trainees interested in maximal muscle growth are probably best off moderating their grain intake because of the otherwise extreme amount of anti-nutrients in the diet that can interfere with protein and mineral digestion. Similarly, the finding that whole grains are no better for fat loss than processed grains in spite of being less digestible, having more fiber and having more protein suggests that grains may not be as fat loss friendly as the Federal Department of Agriculture would have you believe.