Why is peanut butter so popular in fitness?

Peanut butter is one of the classic bodybuilding and fitness foods, acquiring the reputation of a “must-have” for anyone who seriously approaches these types of activities. The reasons behind this reputation, however, do not seem very strong.

This simple article tries to shed light on the common justifications and fallacies behind the acceptance of peanut butter as a useful food for physical improvement.

Introduction

When peanut butter entered the selection of classic gym-goers’ foods is unclear, but some clues suggest this was already widespread in bodybuilding since at least the 1970s, as shown by an example of the American bodybuilder’s diet Casey Viator (1).

It is reasonable to assume that, being peanut butter born in the United States in the late 1800s (2) – which is also the homeland of bodybuilding – and thanks to its “healthy” nutritional profile, over time it became rooted in the tradition of American bodybuilders’ diet, but without there being a specific motivation behind it.

This tradition has made it one of the classic foods for the “bulk” phases, leading the supplement industry to propose “special” peanut butters enriched with other ingredients for gaining muscle mass or use it as an ingredient or flavoring for various products such as powders and protein bars. Accordingly, also fitness and bodybuilding magazines, books, and websites have solidified the perception of ideal food for these activities.

Peanut butter contains “good fats”

One of the most popular reasons to justify the inclusion of peanut butter in the diet is its content of “good fats”. This vague term is generally used in popular jargon to define the broad class of unsaturated fats (UFAs), as there is still a false belief that saturated fats (SFAs) have deleterious health effects regardless, and that foods containing them wouldn’t have any beneficial effects.

Peanuts are composed of ~50% monounsaturated fat, ~30% polyunsaturated fat, and ~15-20% saturated fat (2); in other words, about 80-85% of fats are unsaturated, in line with the fat profile of most other nuts and seeds. While this would confirm its reputation as a source of “good fats”, the term is simplistic when viewed in relative terms and in a real-world context.

Nutrition guidelines first do not recommend avoiding saturated fat, but to not (habitually) exceed 10% of caloric intake (a little less than 30 g in a 2500 kcal diet) (3). Additionally, many foods with high saturated fat content (such as many dairy products or cocoa) may have a beneficial effect on health (3). In other words, saturated fat is unhealthy or bad if eaten in excess and/or through the wrong foods, as can be for some of the unsaturated fats.

More importantly, peanuts are certainly not the only source of these “good fats” (UFAs) since many other nuts and seeds have an equally if not more interesting fat profile. There are butters or creams based on other nuts and seeds (such as almonds, hazelnuts, cashews, pistachios, etc.) that can be considered as an equally valid alternative, not to mention other sources of these fats other than nuts and seeds.

Peanut butter is useful for bulking phases

One of the most classic arguments is that peanut butter would be a “must-have” in the bulk phases to add calories and help build muscle, perhaps implying that their “good fats” content would limit body fat gain.

The perception of “less fattening” food is likely due to the typical health halo bias (4), whereby when a food is or is only perceived as healthy, its potential unfavorable characteristics are ignored or minimized.

The idea of ​​using peanut butter as one of the many means of adding calories is valid, but it’s certainly implausible that it has properties in itself anabolic, or that it limits body fat gain with the same calorie excess and total dietary fat.

Some research has suggested that polyunsaturated fat is more anabolic and less obesogenic than saturated fat (5). Beyond the limitations (6) and the need for further replications, that could suggest that monounsaturated fat, of which peanuts are richer, might also have similar benefits. But even if these advantages existed, they would not be exclusive to peanut butter, but to unsaturated fats in general, which can derive from a myriad of other food sources.

In other words, whether or not peanut butter is present in a diet for increasing muscle mass wouldn’t make any difference, with the same calories, macronutrients, and unsaturated fats in the diet. If anything, the relative problem would be only if the fats it contains were entirely replaced by saturated ones, and if the latter exceeded the 10% limit of caloric intake, but this is rather unlikely.

Peanut butter contains a lot of protein

The high protein content is another of the classic arguments supporting the usefulness of peanut butter for physique goals. This food has about 25% protein, a relatively high percentage like many other legumes and nuts.

But a common misconception is that legumes (of which peanuts are part) have a protein content similar to meat or fish when the latter has much more protein; cooked meat and fish have approximately double the protein compared to peanuts or its butter, and have 3-4 times more when compared with approximately the same hydration state (i.e. on dry weight).

The protein quality of peanut protein is not particularly high (7), being deficient in some essential amino acids such as cysteine, methionine, threonine, lysine, isoleucine, and valine (8) (especially lysine). It is likely no coincidence that peanut protein doesn’t appear to have been proposed by supplement industry to produce protein powders, as is happening more and more for many other plant sources (9,10). A point in favor is that butter, the product of a refining process, at least improves the food absorption (and therefore its protein) compared to the whole form (11).

Even though the protein content is in a modest percentage, the problem is that to get enough protein (20-25 g) from peanuts alone, it would be necessary to consume about 80-100 g (2.8-3.5 oz), amounts that would at the same time provide 40-50 g of fat (that can be half up to 80-100% of the total fat requirement for many people and dieting athletes). Peanuts and their butter should therefore not be viewed as a “protein food”, since the portions normally eaten in order not to exceed with fat, do not even provide many protein (just 5-7 g), much less of high quality. Peanut butter just provides a little extra protein to those that should already be present in the meal with a concentrated, high-quality protein food.

Peanut butter is a healthy food

The last vague notion supporting the use of peanut butter in fitness relies on the rhetoric that after all, it’s a healthy food, rich in vitamins, minerals, fiber, antioxidants, and again, “healthy” unsaturated fats. Although these are all true notions (2), these same arguments could apply to any other healthy food, nut, or derived butter, without confirming a specific usefulness of peanut for bodybuilding or aesthetic improvement.

A problem with peanut butter, as well as with butters from nuts and seeds in general, is their high-calorie density (low water content and high fat content); that makes their satiating properties per calorie disadvantageous, making them at high risk of exceeding with calories if not tracked. The fact that a food has good inherent nutritional properties does not, therefore, exclude that it may also have disadvantageous characteristics for many people.

Since excess calories and increased body fat in themselves worsen health parameters (12), the impact of peanut butter on health is related to the person’s environmental (energy) context and food education. For those who don’t have a good dietary control and want to keep weight under control, whole peanuts would be much more suitable, since they are less absorbed than their butter (11) and tend to not promote weight gain (13) (this also applies to other nuts and seeds).

An experiment: the Antonio et al. study (2018)

Since peanut butter is a classic in bulk nutrition for bodybuilders, a recent study mimicked these conditions to verify the long-term effects of the calorie surplus given by the food on body composition in those who regularly train with weights (4).

José Antonio (the CEO of the ISSN) and colleagues involved a group of 17 resistance-trained men and women, giving them ~450 g (16 oz) of peanut butter daily, for a caloric surplus of ~500 kcal, over 4 weeks. At the end of the study period, the group gained an average body fat of 800 g (1.7 lbs) (4). Even with some limitations (such as low sample and poor energy balance control), this suggests that in a realistic bulking situation, a lot of peanut butter does not prevent body fat gain in those who train with weights.

One criticism that can be expressed about this study is that it didn’t compare the calorie excess from peanut butter with the same calorie excess given by other foods. This, therefore, does not provide an answer to the common perception that peanut butter is “less fattening” than other foods. Considering that dietary fat has a high obesogenic capacity, and that butter is more absorbed than whole peanut (albeit a little less than its oil) (11), this hypothesis is implausible. On the contrary, various evidence suggests that adding moderate portions of whole seeds to the diet (20-60 g/day) does not contribute to weight gain (13).

Conclusions

Peanut butter is associated with the classic diet of bodybuilders and fitness enthusiasts, but the reasons for this tradition don’t appear to have a rational basis.

This is probably because this food was born in the United States, the homeland of bodybuilding, and since it has good nutritional characteristics to be a tasty high-calorie snack, this has been accepted by bodybuilders, always careful to select high-quality foods.

Surely peanut butter can be considered a healthy food rich in useful nutrients (high nutrient density), but it’s nothing “magic” or indispensable for optimizing physique results, nor irreplaceable with other foods with a similar nutritional profile. For example, there are butters or creams from other nuts and seeds which are a valid alternative with similar nutritional qualities.

Whether it is affecting health or fitness, for those who control calories and macronutrients and like it as a food, peanut butter is a sensible option as hundreds of other foods can be. For those who have to control weight and do not have the habit or the will to track calories and macronutrients, peanut butter needs to be evaluated with caution due to its high-calorie density and therefore the strong probability to provide a calorie excess in the diet. There are intermediate cases between these two extremes, but for those who tend towards overweight, there are more suitable foods, starting with whole nuts and seeds.

Riferimenti:

1. Petrillo OM, Schipani F. The Secret Book Of Old School Training. Lulu.com. 2014.
2. Arya SS et al. Peanuts as functional food: a review. J Food Sci Technol. 2016 Jan;53(1):31-41. 
3. Astrup A et al. Saturated fats and health: A reassessment and proposal for food-based recommendations: JACC state-of-the-art review. J Am Coll Cardiol. 2020 Aug 18;76(7):844-857.
4. Antonio JA et al. The effect of peanut butter overfeeding in trained men and women: a pilot trial. J Exerc Nutr. 2018;1(3).
5. Rosqvist F et al. Overfeeding polyunsaturated and saturated fat causes distinct effects on liver and visceral fat accumulation in humans. Diabetes. 2014 Jul;63(7):2356-68. 
6. The Rosqvist study compared saturated fat with polyunsaturated fat, while peanut fats are predominantly monounsaturated. Only lean mass was measured and not muscle mass specifically, in subjects who did not train. This does not prove an anabolic effect on muscle, nor does it prove it for peanuts or its butter.
7. Hoffman JR, Falvo MJ. Protein – Which is best? J Sports Sci Med. 2004 Sep; 3(3): 118–130. 
8. Diby NAS et al. Improving peanut protein quality: Expression of a synthetic storage protein. Afr J Biotechnol. 2020 May;19(5): 265-275.
9. Jäger R et al. International Society of Sports Nutrition Position Stand: protein and exercise. J Int Soc Sports Nutr. 2017 Jun 20;14:20.
10. Gorissen SHM et al. Protein content and amino acid composition of commercially available plant-based protein isolates. Amino Acids. 2018 Dec;50(12):1685-1695.
11. Levine AS, Silvis SE. Absorption of whole peanuts, peanut oil, and peanut butter. N Engl J Med. 1980 Oct 16;303(16):917-8.
12. Bray GA, Bouchard C. The biology of human overfeeding: A systematic review. Obes Rev. 2020 Sep;21(9):e13040.
13. Guarneiri LL, Cooper JA. Intake of nuts or nut products does not lead to weight gain, independent of dietary substitution instructions: A systematic review and meta-analysis of randomized trials. Adv Nutr 2020 Sep;00:1–18.