Posted on by Joy Y. Erdile, MSc, RD

Could Protein be the Appetite’s Control Mechanism

Introduction

The idea that there is a specific food that acts as the “off switch” for appetite is very compelling. Who hasn’t eaten more food than they planned or wanted? Whether it was too much of the same food or too much of a variety of foods, we often eat until we are stuffed. Wouldn’t it be amazing if we could eat something that could satisfy that drive to eat? According to Dr. Stephen Simpson and Dr. David Raubenheimer, that “something” is protein.

The Protein Leverage Hypothesis

In their 2005 paper published in Obesity Reviews, Simpson and Raubenheimer proposed that obesity isn’t primarily caused by eating too much fat, or eating too many ‘carbs’, but by eating food that has too little protein [1]. They called this the “Protein Leverage Hypothesis”. This states is that humans have a built-in appetite for protein that drives food consumption. When we eat food that contains low an amount, we will over-eat until the amount we need is met.

Evolutionary Perspectives and Nutritional Transition

In paleolithic times, the human diet was ~35% animal protein, 33% fat and the remainder plant material (which was limited in the diet due to antinutrients such as phytates, oxalates, tannins, trypsin-, amylase-, and protease inhibitors, and glycosides) [2]. Humans evolved and thrived eating this way.

In contrast, currently the percentage of protein in diets around the world remains at ~16% of daily calories [3] and Simpson and Raubenheimer believe that it is this ‘protein dilution’ of the diet that results in us overeating food, to try and obtain sufficient amounts.

In their 2005 paper, they wrote;

”The obesity epidemic is among the greatest public health challenges facing the modern world. Regarding dietary causes most emphasis has been on changing patterns of fat and carbohydrate consumption. In contrast the role of protein has largely been ignored because (i) it typically comprises only approximately 15% of dietary energy and (ii) protein intake has remained near constant within and across populations throughout the development of the obesity epidemic. We show that paradoxically these are precisely the two conditions that potentially provide protein with the leverage both to drive the obesity epidemic through its effects on food intake and perhaps to assuage it. [1]”

What this implies is, if we don’t intentionally prioritize protein in the diet, we will overeat fat and carbohydrate to reach the amount we require (or have evolved to eat).

Dopaminergic Response to Ultra-Processed Foods

To complicate matters, the food environment is made up of ultra processed foods that are mostly carbohydrate and fat. Snack and convenience foods were only introduced the early 1970s — which, coincidently was when the obesity epidemic began.

We have known since 2018 that foods high in both carbohydrate and fat result in more dopamine being released from the reward-center in striatum of our brain, than foods with carbohydrate alone, or fat alone [4]. This is why will often overeat French fries, but rarely a baked potato. Perhaps, the fact that snack and convenience foods are so low in protein is a contributing factor to us overeating them.

Current statistics indicate that 55% of calories eaten by adults [5] and 67% of calories eaten by children and teenagers [6] come from ultra-processed foods — high in both carbohydrate and fat, and low in protein.

A 2018 follow-up paper by Simpson and Raubenheimer based on the 2009-2010 National Health and Nutrition Examination Survey (NHANES) found higher consumption of ultra-processed foods was associated with lower protein density [7].

“Consistent with the Protein Leverage Hypothesis, increase in the dietary contribution of ultra processed foods was also associated with a rise in total energy intake, while absolute protein intake remained relatively constant [7].

“The protein-diluting effect of ultra processed foods might be one mechanism accounting for their association with excess energy intake [7].”

Rather than going in circles arguing whether eating too much fat or eating too many carbs resulted in obesity, perhaps it is more productive to focus on ensuring sufficient intake of high quality protein.

The RDA – Enough Protein to Prevent Deficiency

But how much is best? It depends for whom.

The Recommended Daily Allowance (RDA) for any nutrient is the average daily dietary intake level that is sufficient to meet the needs of 97-98 % of healthy people. The RDA is not the optimal requirement, but the absolute minimum to prevent deficiency.

The RDA for healthy adults is calculated at 0.8 g protein / kg of body weight [8]. A sedentary 70 kg / 154 pound man needs a minimum of 56 g and a sedentary 60 kg / 132 pound woman needs a minimum of 48 g protein per day.

Protein Needs for Active Healthy Adults

For physically active adults, the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine [9] recommend an intake of 1.2—2.0 g protein / kg per day to optimize recovery from training, and to promote the growth and maintenance of lean body mass.

Protein Needs for Older Adults

Several position statements by groups working with an aging population indicate that intake between 1.0 and 1.5 g protein / kg per day may best meet the needs of adults during aging [10, 11].

For the average, healthy 70 kg / 154 pound sedentary man this would be daily protein intake of 70 -105 g per day and for the average, healthy 60 kg / 132 pound sedentary woman this would be an intake of 60-90 g protein per day.

Clinical Range of Safe Intake

As written about in an earlier article, according to Dr. Donald Layman, PhD, Professor Emeritus, of Nutrition from the University of Illinois, the highest end of the range of safe intake of protein is 2.5 g protein/ kg per day.

For the average 70 kg / 154 pound sedentary man this would be a maximum daily protein intake of 175 g per day and for the average 60 kg / 132 pound sedentary woman, this would be a maximum protein intake of 150 g/ day.

Final Thoughts…

We know that the presence of both carbs and fat together in a food has a supra-additive effect on the pleasure center of our brain [4]. This leads to us eating way more of these foods, than foods with just carbs or just fat. Given this, it would make sense to avoid foods that have high amounts of both carbs and fat which include almost all of our favourite snack and convenience foods.

With the exception of nuts, seeds and milk most real, whole food is high in either carbs or fat, not both. Aim to eat these foods the most, but not together at the same meal.

Based on the Protein Leverage Hypothesis, aim to eat sufficient high protein foods based on your individual needs. Reach for foods such as salmon, tuna, skinless chicken and shrimp the most often. These contain 8 grams of protein per ounce (28 g) and 1.5 grams of fat. Enjoy a good ribeye, some pork or chicken legs that have on average 6.2 grams of protein per ounce (28g), and 6g of fat.

Vegetarian? No problem!

Cottage cheese has 28 g of highly bioavailable protein per cup, and Greek yogurt has 16 grams of protein per cup. Tofu only has ~4.7 grams of protein per ounce (28g), and is a complete protein containing all the essential amino acids.

Think of protein as a control button for appetite and reach for the types of protein that suit your lifestyle best!

More Info

If you would like more information about how I can help you please send me a note through the Contact Me form.

To your good health!

Joy

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References

  1. Simpson SJ, Raubenheimer D. Obesity: the protein leverage hypothesis. Obes Rev. 2005;6(2):133-142. doi:10.1111/j.1467-789X.2005.00178.x [https://pubmed.ncbi.nlm.nih.gov/15836464/]
  2. Ben-Dor M, Gopher A, Hershkovitz I, Barkai R. Man the Fat Hunter: The Demise of Homo erectus and the Emergence of a New Hominin Lineage in the Middle Pleistocene (ca. 400 kyr) Levant. PLoS ONE. 2011;6(12):e28689. [https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0028689]
  3. Lieberman HR, Fulgoni VL 3rd, Agarwal S, et al. Protein intake is more stable than carbohydrate or fat intake across various US demographic groups and international populations. Am J Clin Nutr. 2020;112(1):180-186. doi:10.1093/ajcn/nqaa088 [https://pubmed.ncbi.nlm.nih.gov/32390035/]
  4. DiFeliceantonio AG, Coppin G, Rigoux L, et al. Supra-Additive Effects of Combining Fat and Carbohydrate on Food Reward. Cell Metab. 2018;28(1):33-44.e3. doi:10.1016/j.cmet.2018.05.018 [https://pubmed.ncbi.nlm.nih.gov/29909968/]
  5. Zhang Z, Jackson SL, Martinez E, et al. Association between ultraprocessed food intake and cardiovascular health in US adults: a cross-sectional analysis of the NHANES 2011-2016. Am J Clin Nutr. 2021;113(2):428-436. doi:10.1093/ajcn/nqaa276 [https://pubmed.ncbi.nlm.nih.gov/33147565/]
  6. Wang L, Martínez Steele E, Du M, et al. Trends in Consumption of Ultraprocessed Foods Among US Youths Aged 2-19 Years, 1999-2018. JAMA. 2021;326(6):519-530. doi:10.1001/jama.2021.10238 [https://jamanetwork.com/journals/jama/fullarticle/2782866]
  7. Martínez Steele E, Raubenheimer D, Simpson SJ, et al. Ultra-processed foods, protein leverage and energy intake in the USA. Public Health Nutr. 2018;21(1):114-124. doi:10.1017/S1368980017001574 [https://pubmed.ncbi.nlm.nih.gov/29032787/]
  8. Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press; 2005. [https://nap.nationalacademies.org/catalog/10490/dietary-reference-intakes-for-energy-carbohydrate-fiber-fat-fatty-acids-cholesterol-protein-and-amino-acids]
  9. Thomas DT, Erdman KA, Burke LM. American College of Sports Medicine Joint Position Statement. Nutrition and Athletic Performance. Med Sci Sports Exerc. 2016;48(3):543-568. doi:10.1249/MSS.0000000000000852 [https://pubmed.ncbi.nlm.nih.gov/26891166/]
  10. Fielding RA, Vellas B, Evans WJ, et al. Sarcopenia: an undiagnosed condition in older adults. Current consensus definition: prevalence, etiology, and consequences. International working group on sarcopenia. J Am Med Dir Assoc. 2011;12(4):249-256. doi:10.1016/j.jamda.2011.01.003 [https://pubmed.ncbi.nlm.nih.gov/21527165/]
  11. Bauer J, Biolo G, Cederholm T, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc. 2013;14(8):542-559. doi:10.1016/j.jamda.2013.05.021 [https://pubmed.ncbi.nlm.nih.gov/23867520/]
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