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Discover the Healthiest Sources and Amounts of Protein! Current Research

Plant-based Diets, Entomophagy, and Evidence

What is the optimal amount of protein for health and performance? Cut through the hype, learn the truth according to current research (Image credit: Ashutosh Sonwani at Pexels)

Protein!!! It seems everyone is obsessed with “getting enough” protein nowadays. If you eat plant-based, the number one question you get is “where do you get your protein?” Athletes, and increasingly, non-athletes, slog down protein shakes–convinced that such is necessary for health and fitness goals.

Even in the plant-based world, icons for the plant-based movement frequently note “you can get all the protein you need eating plants.” Often, plant-based movement icons note that protein needs are exaggerated by marketers, etc. Yet many of them consume highly processed plant-based protein powders. With so many opinions and apparent contradictions, an evaluation of the current research can be helpful.

What does the research-based, current evidence actually say about protein needs–including for athletes? What daily amount is the right amount? Does it matter where you get your protein in terms of health outcomes? Are high-protein diets healthy? What does the evidence say?

Protein sources & Health: Animal, plant, does it matter?

Sources of protein–animal versus plants, does it matter? Eggs, yogurt, cheese, milk, chicken, fish…or legumes, beans, whole grains, nuts–as long as you stay away from evil fatty, red, or processed meats, does protein source really make a difference in your health according to research? Yes, it does matter–according to a growing body of high-quality research.

In research published in The European Journal of Epidemiology, 7786 participants of the “Rotterdam Study” in the Netherlands were analyzed for dietary patterns and mortality (death) rates. The meta-analysis (where multiple studies are combined and findings analyzed in totality) was conducted for a time span covering nearly 30 years (Zhang, Moumdjian, Gonzalez-Jaramillo, van der Schaft, Bramer, Ikram, & Voortman, 2020). A sub-analysis of the data collected evaluated the impact of protein source (animal versus plant) and all-cause mortality rates along with cardiovascular disease death rates.

As animal protein intake increases, so does mortality rate: Plant protein has the opposite effect

Researchers found that for every 5% increase in animal protein intake (as a percentage of total caloric intake), there was a measurable and significant increase in cardiovascular deaths and overall mortality rates. Those with the highest animal protein intake experienced a 12% higher mortality rate from all causes versus those with the lowest animal protein intake. Protein from meat and dairy strongly influenced the increase in cardiovascular mortality rates (Zhang et al., 2020). Protein from eggs and fish did not appear to impact mortality rates.

High protein intake from animal sources, such as meat and dairy, corresponded with increased deaths from all causes, particularly cardiovascular causes (Image credit: Andrey Niqi at Pexels)

Conversely, as protein intake from plant sources (legumes, nuts, vegetables) increased in percentage of total caloric intake, significant REDUCTIONS in mortality rates were noted. Every 3% increase in protein intake from specifically legumes, nuts, vegetables, and fruits (but not grains) resulted in 25% reductions in overall mortality rates during the study period (Zhang et al., 2020).

Bad news for keto enthusiasts: “Evil high-carb” legumes apparently protect you from premature death

Separately, the researchers also performed a meta-analysis on high quality, prospective cohort studies (studies where participants with similarities at the beginning of a study are followed over time to evaluate differences in outcomes and potential causes of such differences). This analysis included data from 350,452 participants and 11 studies, with time periods of the studies covering anywhere from 12 to 28 years. Once again, higher total protein intake, particularly intake from animal protein sources, was associated with higher rates of mortality with a 9% increase in deaths due to cardiovascular disease. The lower quartile of participants took 4.3% of their daily energy from animal protein, with the highest quartile consuming 20% of their daily energy from animal protein sources.

Those with the highest plant protein intake, on the other hand experienced a 7% reduction in all-cause mortality rates and a 14% reduction in cardiovascular death rates (Zhang et al., 2020). Researchers noted that the nature of amino acids found in animal products (branched-chain and aromatic amino acids) differ from those found in plants (which are low in branched-chain and aromatic amino acids). Amino acids in animal products appear to contribute to insulin resistance, obesity, and thereby, increased cardiovascular disease risk (Zhang et al., 2020).

Interestingly, fish, eggs, and grains were neutral, neither protective or particularly harmful (Zhang et al., 2020). This supports findings in the Blue Zones territories where the longest living, healthiest population groups ate scant meat. Frequently, these populations included only up to 3 eggs per week and small amounts of fish in their diets–plant nutrition being their dominant source of protein and caloric intake (Bluezones.com, 2020).

Protein amounts: How much do you need? It depends on your goals

According to the journal Food & Function published by the Royal Society of Chemistry, sedentary yet healthy adults need as little as 0.8 grams of protein per kilogram of body weight (Wu, 2016). In order to calculate your own protein needs if you are a sedentary (minimally active adult) and you live in the U.S., first divide your body weight in pounds by 2.2 to convert your body weight to kilograms.

185 lbs / 2.2 = 84 kgs (My body weight in kilograms)

So pretend I was not very physically active, at 185lbs (84kg), my daily protein requirements to maintain general healthy bodily functions would equate a mere 67 grams per day. Divided into 4 meals (snacks included as “meals”), I would only need 17 grams of protein per meal. This is easily achieved following a plant-based diet. Just 2 pieces of whole grain bread have 10 grams of protein! Add a handful of nuts or soup with beans and the target is easily achieve, no meat, no protein shakes, no dairy required. This applies to the nearly 1 in 4 adults in the U.S. (Americashealthrankings.org, 2020). For those desiring to maximize skeletal muscle tissue and minimize white fatty tissue, protein amounts of 1.4 grams/ kg are determined to be useful per research (Wu, 2016).

Health promoting proteins from beans, nuts, and legumes are useful in meeting daily protein goals (Image credit: Frans Van Heerden at Pexels)

As activity increases from mild to moderate to intense, protein needs increase to 1 gram / kg, then 1.3 grams/ kg, then 1.6 grams / kg respectively (Wu, 2016). Using my body weight again as an example, my protein needs with mild activity (such daily mild cardio training) would be 84 grams total, rising to 134 grams daily if I were to be very physically active (which I am). Divided into 4 meals, 33 grams of protein per meal is required for optimal health for a 185lb male. This too is achievable without supplements, powders, or meat, though selection of high protein plant foods (such as lentils, beans, whole grains, nuts, and high protein pasta) is necessary to achieve these numbers.

What if you are an athlete or weight train?

A frequently touted number for protein intake requirements for athletes is simplified to be approximately 1 gram of protein for every pound of body weight (if you live in the U.S.) or 1.8 grams of protein per kilogram (if you live pretty much anywhere else). Some plant-based enthusiasts argue that amount is excessive. Some weight training enthusiasts argue that amount is too low. What does the research say?

Guidelines for athletes who resistance (weight) train: Research suggests you may need less than you think

According to the “International Society of Sports Nutrition Position Stand,” the daily recommended amount of protein advised for building and maintaining muscle mass ranges from 1.4 grams/ kg – 2 grams / kg based on current research evidence (Jäger et al., 2017). Twenty to 40 grams of this total protein requirement needs to come from high quality protein (such as protein rich in leucine…a plant-based example being beans). This amount is somewhat less than 1 gram per pound of body weight. In order to calculate your own protein needs if you live in the U.S., first divide your body weight in pounds by 2.2 to convert your body weight to kilograms.

Next, multiply your weight x 1.4 grams to find the low range for your daily protein intake needs, or by 2 grams to find the upper range. According to the guidelines, this protein amount should be divided into multiple meals separated by 3 to 4 hours (Jäger et al., 2017). With my body weight of 185 lbs, my protein requirements to build and maintain muscle (paired with resistance training) would be as follows:

185 lbs / 2.2 = 84 kgs (My body weight in kilograms)

84 kgs x 1.4 grams protein / kg = 118 total grams of daily protein needed to maintain and build muscle according to research. Note, this is substantially less than 185 grams (1 gram per pound) suggested frequently by muscle magazines and other popular sources!!! Try the calculation yourself for your own body weight!!!

Protein requirements are increased for those that lift weights or engage in intense activity levels, but still lower than many believe (Image credit: Victor Freitas at Pexels)

Divided into 4 meals, this comes to about 30 grams per meal. This amount of protein is easily achieved following a plant-based diet without the use of protein powders. Whole grain pastas with beans and sauce on top, peanut butter sandwiches on whole grain bread with a lentil soup, etc are options that can help achieve an intake over 30 grams per meal. My plant-based, whole foods smoothie in the morning has nearly 50 grams of protein alone with no protein powders added.

At the upper end for muscle maintenance and building, 84 kgs x 2 grams protein/ kg = 168 total grams of daily protein required for my body weight of 185 lbs. This still amounts to less than the 1 gram per pound calculation touted by mainstream sources, but does result in requirements of 42 grams per 4 meals. Such an amount is doable, but a little more difficult to achieve when using strictly plant-based natural sources (excluding protein powder shakes). An option is to eat 5 meals per day instead of 4, bringing requirements down to 34 grams per meal. Another option is to incorporate protein powders, though they seem unnecessary at the lower ranges provided for building and maintaining muscle when resistance training.

Guidelines may be higher than you think if you are in a calorie deficit and want to keep muscle

During periods of calorie deficits (such as “dieting,” or “cutting”) the body enters a catabolic state where both muscle tissue and fat are lost. To reduce or avoid muscle loss during a period of low caloric intake, the International Society of Sports Nutrition recommends higher protein intakes. Recommendations for preserving muscle tissue during low calorie “cutting” phases equates 2.3 – 3.1 grams / kg / day.

Using my weight again as an example, at 185lbs (84 kgs), this would equal 193.2 grams of protein on the low end to 260 grams on the high end. Divided into five meals per day, approximately 40 grams to 52 grams would be required per meal. Doing this “naturally” without the use of protein shakes or lean animal protein sources while maintaining a caloric deficit would be admittedly difficult.

Chronic, very high protein intakes are not conducive to long term health

It MUST BE NOTED that such a high protein intake (over 2 grams/ kg) is NOT conducive to long term health according to current research (Wu, 2016). Chronically elevated protein intake levels (such as those frequently touted by mainstream popular magazines) are associated with digestive, kidney and vascular abnormalities (Kalantar-Zadeh, Kramer, & Fouque, 2020; Wu, 2016). While protein ingestion at rates over 2 grams/ kg may serve short term interests, they are recommended against for the long term (Wu, 2016). Such high intakes are generally unnecessary, even for highly active adults as noted in the research above.

Summary

What are your protein needs? If you are a generally healthy adult, just find your weight in kg and multiply the recommended protein amounts based on your activity levels and goals. According to the research cited above, the appropriate protein amount in grams appears to be as follows (based on personal activities and goals):

Your weight in kg x 0.8: If you are sedentary
Your weight in kg x 1.0: If you do mild/ light activity (activity levels can be determined by clicking here)
Your weight in kg x 1.4: If you do moderate activity and/ OR if you desire to improve your muscle to fat ratio (such as in fighting obesity)
Your weight in kg x 1.6: If you do intense activities including weight training/ resistance training (up to your weight in kg x 2.0)
Your weight in kg x 2.3 (up to 3.1): If you weight train/ resistance train and are in a “cutting” phase, such as during a temporary calorie deficit
No more than your weight in kg x 2.0 over the long term: to preserve long term kidney, digestive, and vascular health.

Further, based on research, the majority of your protein should come from plant-based sources if you are interested in long term health and prevention of premature mortality. For most people, protein powders are unnecessary though they may be convenient. Protein powders may come with their own risks, such as containing high levels contaminants and unknown long term health impacts (Harvard University, 2018). Protein intake requirements are dependent on your activity levels and goals, though frequently research-based intake requirements are lower than reported in popular magazines, books and websites.

Thanks for reading!!! I hope you found this article informative! Feel free to leave a comment, and/ or sign-up to receive email notice of new articles!!! Sincerely, Donovan

References

Americashealthrankings.org. (2020). Physical inactivity. Retrieved from https://www.americashealthrankings.org/explore/annual/measure/Sedentary/state/ALL

Bluezones.com. (2020). Food guidelines. Retrieved from https://www.bluezones.com/recipes/food-guidelines/

Harvard University. (2018). The hidden dangers of protein powders. Retrieved from https://www.health.harvard.edu/staying-healthy/the-hidden-dangers-of-protein-powders

Jäger, R., Kerksick, C. M., Campbell, B. I., Cribb, P. J., Wells, S. D., Skwiat, T. M., Purpura, M., Ziegenfuss, T. N., Ferrando, A. A., Arent, S. M., Smith-Ryan, A. E., Stout, J. R., Arciero, P. J., Ormsbee, M. J., Taylor, L. W., Wilborn, C. D., Kalman, D. S., Kreider, R. B., Willoughby, D. S., Hoffman, J. R., … Antonio, J. (2017). International Society of Sports Nutrition Position Stand: Protein and exercise. Journal of the International Society of Sports Nutrition, 14, 20. https://doi.org/10.1186/s12970-017-0177-8

Kalantar-Zadeh, K., Kramer, H. M., & Fouque, D. (2020). High protein diet is bad for kidney function. Nephrology Dialysis Transplantation, 35(1), 1-4. Retrieved from https://www.medscape.com/viewarticle/924423?nlid=134117_785&src=WNL_mdplsfeat_200225_mscpedit_nurs&uac=223310AV&spon=24&impID=2291225&faf=1

Wu, G. (2016). Dietary protein intake and human health. Food & function, 7(3), 1251-1265. https://doi.org/10.1039/C5FO01530H

Zhang, X., Moumdjian, A. C., Gonzalez-Jaramillo, V., van der Schaft, N., Bramer, W. M., Ikram, M. A., & Voortman, T. (2020). Dietary protein intake and all-cause and cause-specific mortality: results from the Rotterdam Study and a meta-analysis of prospective cohort studies. European journal of epidemiology, 10.1007/s10654-020-00607-6. Advance online publication. https://doi.org/10.1007/s10654-020-00607-6

A Brief Commentary on Popular Diet Trends and their Absurdities

Plant-based Diets, Entomophagy, and Evidence

Plant-based, Keto, Paleo and “Medium’s”…Making Sense of the Nonsense

“Prove all things, hold fast to that which is good”– 1 Thessolonians 5: 21

This will be a brief commentary on the absurdities upon which many popular diet programs are based. The claims on the surface sound great. These claims sell books. The claims are parroted by coworkers and family members. The claims however are rich in rhetoric and low in evidence in most cases. A little common sense applied to their shallow logic reveals the absurd nature of many popular diet program claims.

Most people realize that something is broken with the standard American diet (abbreviated “SAD” in the literature, how fitting!). Americans struggle with obesity and obesity related illnesses. According to the CDC, nearly 40% of Americans in the U.S. are obese (CDC.gov, 2018). Obesity contributes to development of illnesses such as diabetes, heart disease, premature deaths, certain cancers and as such, also places tremendous burdens on the health care system.

With most people agreeing there is a problem, there is no shortage of persons ready to cash-in with homegrown solutions. Some far out theory, some sexy marketing, appearances on daytime T.V. programs and there you have it, the next big thing until the next, next big thing, comes along. Meanwhile, America’s obesity problem continues to worsen.

Problems Mean Opportunities…and Opportunists…

For an evidence-based diet supported heavily by scientific literature, see my post exploring the evidence on plant-based diets. The evidence clearly favors a plant-based diet for most of us living in the first-world modern era. Those advocating for plant-based diets frequently are equally prone, however, to making their case based on rhetoric as opposed to science.

Without further ado, here are some of the bizarre yet common appeals made for diets:

The meat and animal protein enthusiast: “Eat this way, because its how our paleolithic hunter-gatherer ancestors ate. ”

Oh, ok, makes sense. For most of human history, humans ate a certain way, and so therefore, we should eat that way as well. Sounds good, except for our modern lifestyle has essentially nothing in common with our ancestors. (Contradicting paleo diet claims, true modern hunter-gatherers living traditional hunter-gatherer lifestyles actually eat a diet that is 72% plant based, with only 14% of their diet consisting of protein!! (Brouns, 2018). They also have the lowest level of chronic illness of any population studied to date (Brouns, 2018)).

Should we eat like our ancestors? Are you exposed constantly to the elements, such as either continuous intense heat free of air conditioning (summer or the tropics) or sleep in cold, drafty homes or tents heated by poorly conducting fireplaces or less? Do you hike over great distances, then kill your food and process it by hand ALL THE TIME? Rain, shine, fall, winter, spring, summer? Are you exposed repeatedly to days with no food at all? Do you pack up your belongings, tear down camp, carry everything then set up camp somewhere else as you follow migratory patterns?

Should You Eat Like Your Ancestors? Sounds Great…Assuming You also Face Constant Exposure to the Elements, Hunt, Kill and Process all Your Food by Hand, Eat Once to Twice per Day… if at All…

Truth is, we actually do not know much about how often our ancestors feasted or experienced famine (Berbesque, Marlowe, Shaw, & Thompson, 2014). Instead, all kinds of assumptions are made. Berbesque et al. (2014) notes that modern hunter-gatherer societies do not necessarily reflect the experience of ancient humanity as many of them have been pushed to more resource-poor territories by stronger, wealthier societies in recent history.

Jared Diamond has lived with modern hunter-gatherer tribes and describes his experiences inside his books. A copy of his book can be found here. In the book, The World Until Yesterday (2014), he notes that indigenous people find it amusing and even off-putting regarding how frequently modern first world humans eat within a day. In his book he describes how after everyone ate breakfast, the tribe was surprised when westerners not much later decided it was time to eat lunch. They were somewhat amused. When supper rolled around they were just plain annoyed with these constantly-eating visitors! (Diamond, 2014).

Diamond (2014) describes a day where they hiked an entire day through highlands forest and mountains and had no food, including when they established camp that night. Instead of being angry at him, the New Guineans treated the situation like just another day. Certainly, such fasting or long periods of time even within a single day between meals (intermittent fasting) has been linked to health benefits such as lower diabetes rates and potentially lower cancer rates (Anton et al., 2018).

In other words: You are not your ancestor, you are not a hunter-gatherer. And unless society totally collapses, be thankful you do not have to live like them. If you want their diet to produce the same effects for you (what are those effects anyway?–life expectancy certainly is not longer in these societies as noted by Diamond, 2014), you might as well match their activity levels, fasting frequencies, heat and cold exposures…or maybe you could just see what works for actual modern day people according to the science.

Intermittent Fasting is Likely a Normal Phenomena for Hunter Gatherers as Described by Anthropologist and Author Jared Diamond…

The Vegan Enthusiast: “Humans are not ‘evolved’ or designed to eat meat“–or “it is unnatural for us as a species to eat meat”:

There is actually a lot of science supporting plant-based diets for modern day people living modern day lifestyles. I might suggest the evidence I came across largely supports SOME very small amounts of animal products (see my evidence at a glance post on plant-based diets and also edible insects). As noted above, the healthiest population of humans studied in terms of low levels of chronic illness were a mostly plant-based hunter-gather society (Brouns, 2018). With science on the side of plant-based enthusiasts, there is no need to appeal to bizarre or historically inaccurate claims.

For example, similar to the paleolithic hunter-gatherer arguments, “appeal-to-ancestry” arguments are made by plant-based diet enthusiasts. These enthusiasts claim we evolved from essentially plant-eating species and therefore, meat consumption is new and unnatural for our bodies. In a podcast I listened too, a vegan enthusiast noted that no human child would reach out and try to eat a live chicken, but would try to eat a brightly colored plant item like a fruit or berry–thus proving that eating meat is not inherent in our nature.

The Superiority of Plant-based Diets is Evidence-based…Claims that Eating Meat is “Unnatural”–Not so Much…

However, if indeed meat consumption was so unnatural, it seems strange to me that ancient humans frequently wiped out entire local bird and animal populations shortly after settling into new lands through heavy hunting and consumption–and of course habitat destruction (Diamond, 2005). Further, when settling new areas or lands, people frequently brought along animals such as pigs and chickens and other animals with the express purpose of raising them for food. This happened literally all over the world (Diamond, 2005). For such an unnatural process, meat consumption seems to be pretty universal in archaeological and anthropological research.

As noted above: just because meat consumption is relatively universal among ancestral human groups does not mean it is optimal nowadays. For example, just one serving of meat per week was correlated with an increased risk of diabetes (Vang, Singh, Lee, Haddad, & Brinegar, 2008 as cited in Olfert, & Wattick, 2018). Meat consumption has also has been associated with increased cardiovascular risk (Harland & Gartland, 2016). However, intermittent fasting patterns where 12 or more hours routinely pass between meals have been shown to reduce such risk factors (Anton et al., 2018).

Diamond (2004) Notes Ancient Humans Frequently Hunted and Decimated Wildlife Such as Seabird Populations when Settling into New Territories

As such, it appears under modern conditions plant-based diets improve health outcomes, but it is unclear under pre-modern circumstances that meat was ALWAYS bad for people. In fact, many modern chronic diseases are absent in indigenous populations despite their eating meat (Brouns, 2018; Diamond, 2014). There again, however, indigenous populations are exposed to longer and frequent fasting periods, far greater physical demands, and continuous exposure to the elements. If you are reading this post, chances are, these conditions do not apply to you.

“Diets” as Opposed to Lifestyle Changes

Many people successfully stick to vegetarian diets or plant-based diets their entire life. For those that convert to such diets, many stick with such diets for the remainder of their lives. Research into the world’s healthiest populations reveal that these populations ate very little meat or animal products their entire lives. According to a meta-analysis combining 12 research studies, nearly 70% of people that change their lifestyle to a plant-based lifestyle stay with the change over time (Turner-McGrievy, Mandes, & Crimarco, 2017).

Even when people “cheat” on their vegetarian or vegan diet lifestyle, their weight loss remains significantly greater than their meat eating peers over time, and their fruit and vegetable intake remains substantially higher (Turner-McGrievy, Mandes, & Crimarco, 2017).

The Majority of People that Adopt a Plant-based Lifestyle Stay With It…Fad Diets Like Keto…Not so Much…

Keto diets and low carb diets on the other hand provide short term weight loss and improved insulin sensitivity (as do plant based diets) but are difficult to adhere to with time (Brouns, 2018). Unlike plant-based diets, long term safety and health impacts of keto diets are unknown, or even detrimental (Brouns, 2018). In fact, there is research showing that low carbohydrate diets and keto diets are low in fiber, micronutrients, and can lead to vascular inflammation, elevated homocysteine, vascular stiffness, organ damage and cancer risk increases!!!!! (Brouns, 2018). I cover this topic and current research findings in my post “Keto Diet You Say? No Way! Current Research Findings.”

Food/ Diet/ Health “Mediums”

Some diet trends are so bizarre they barely deserve comment. Health psychics? Medical Mediums? Whaaaaaat? Sciencebasedmedicine.org does a nice take-down of this disappointing and delusional profiteering trend. But hey, celebs like it, so it must be real, right?

We Have Plenty of Evidence for Plant-Based Diets…No Need to “Consult Dead People” or “Mediums” for Advice…

So what is right?

Instead of appealing to mythical proto-humans that ate pure plant-based diets, or to ancient ancestor hunter-gatherer societies for which no real applicable research exists for modern-day humans–why not replicate what already has been shown to work now, among modern humans? Bluezones.com sought to do just that . Why do people in Okinawa, Japan, Seventh Day Adventists in California, or those in Ikaria, Greece seem to live longer on average and age with less ailments than most Americans?

Realistically, we are not going to hunt and gather all year long, without any regard of the elements. Nor are we going to traverse miles of wild terrain, again regardless of the elements, establishing camps as a way of life. We are not going to live in poorly heated, extremely drafty homes that run closer to outdoor temperature levels in the winter time. Most of us are going to have more than one meal per day. You will not find most of us going routinely a day or two with no food.

So our conditions are different than in the past. Why not see what actually works now, as demonstrated already by current, modern populations with lifestyles and diets that are a little more realistic/ feasible/ adaptable for the average, working modern person? What a radical, (absurd?) idea!!!

Plant-based Diets: Fears & Answers: A research-packed post to address fears, myths, and biases people have concerning plant-based diets, providing answers to many of the common misconceptions

Evidence at a Glance: Plant-Based Diet Benefits: A quick overview of the research-backed benefits provided by plant-based diets

References:

Anton, S. D., Moehl, K., Donahoo, W. T., Marosi, K., Lee, S. A., Mainous, A. G., 3rd, … Mattson, M. P. (2018). Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity (Silver Spring, Md.), 26(2), 254–268. doi:10.1002/oby.22065

Berbesque, J. C., Marlowe, F. W., Shaw, P., & Thompson, P. (2014). Hunter-gatherers have less famine than agriculturalists. Biology letters, 10(1), 20130853. doi:10.1098/rsbl.2013.0853

Brouns, F. (2018). Overweight and diabetes prevention: is a low-carbohydrate-high-fat diet recommendable? European Journal of Nutrition, 57(4), 1301–1312. https://doi-org.lopesalum.idm.oclc.org/10.1007/s00394-018-1636-y

CDC.gov. (2018). Adult obesity facts. Retrieved from https://www.cdc.gov/obesity/data/adult.html

Diamond, J. (2005). Collapse: How Societies Choose to Succeed or Fail. New York, NY: Viking Press

Diamond, J. (2014). The World Until Yesterday. New York, NY: Viking Press

Harland, J., & Garton, L. (2016). An update of the evidence relating to plantbased diets and cardiovascular disease, type 2 diabetes and overweight. Nutrition Bulletin, 41(4), 323–338. https://doi-org.lopesalum.idm.oclc.org/10.1111/nbu.12235

Olfert, M. D., & Wattick, R. A. (2018). Vegetarian Diets and the Risk of Diabetes. Current diabetes reports, 18(11), 101. doi:10.1007/s11892-018-1070-9

Turner-McGrievy, G., Mandes, T., & Crimarco, A. (2017). A plant-based diet for overweight and obesity prevention and treatment. Journal of geriatric cardiology : JGC, 14(5), 369–374. doi:10.11909/j.issn.1671-5411.2017.05.002