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Written By: Dr. Barry Sears Creator of the Zone Diet

Written by Dr. Barry Sears
on October 17, 2018

Protein is an essential nutrient for human nutrition. However, getting adequate protein in the diet hasn’t always been easy. 

 A Step Back in Time

The first breakthrough for increasing protein intake in our ancestors happened about 700,000 years ago. This occurred when they learned how to use fire to help break down collagen to make it  dramatically easier to access the protein found in raw meat. This also coincided with a significant increase in brain size. This was most likely due to the decrease in the amount of metabolic energy needed to digest protein (1). At the same time, there was a dramatic increase in the development of a number of gene transcription factors (these are also proteins) that allowed our pre-human ancestors greater flexibility in turning their genes on and off with greater speed to make them more flexible to changing environmental conditions (2). This is also likely to have come from increased protein consumption from cooked meat. 

The Next Evolution: Protein Powders

The next major evolution in protein occurred about 70 years ago with the development of isolated protein powders from milk and plants (primarily soy). This allowed the manufacturing of a much wider number of protein-fortified food products such as infant formulas, protein-based shakes and bars, and the ever-increasing array of protein-fortified foods that are so ubiquitous today. Yet this next evolution of protein did not alter the location in the gut that protein is actually absorbed. This is important since the location of where protein is absorbed in the gut can dramatically change its hormonal responses, especially those that are related to the generation of satiety hormones that signal directly to the brain to tell you to stop eating.

 How Protein Gets Absorbed

Regardless, if you are eating animal protein, vegetable protein, or Greek yogurt, the location of where that protein is absorbed remains the same. To illustrate, sometimes a picture is worth a thousand words.

The Science of Protein Digestion


Your small intestine is divided into three sections. The first section is the duodenum where the final digestion of dietary protein is done by enzymes released by the pancreas. This helps to break the protein into small fragments (tri-peptides or even smaller fragments) that can be safely absorbed by the gut without causing an adverse immune response in the body. For individuals with leaky gut, larger fragments of protein can potentially enter into the blood where the body recognizes them as foreign and mounts an inflammatory response as a result of their presence. This is the primary reason for protein allergies like those caused by egg, nuts, and even gluten.

Regardless of the protein source (animal or vegetable), most protein is absorbed in the midsection of the gut (the jejunum). This is fine for getting protein into the body, but not for the maximum generation of the hormonal signals that tell you to stop eating. These signals are released from a small group of cells (called L-cells) that line the interior of gut and release satiety hormones (such as PYY and GLP-1) when activated by protein. The highest concentration of these L-cells is located in the last segment of the gut, the ileum. This means the potential satiety coming from your dietary protein may only be a fraction of what it could be. If you could possibly get more protein to the L-cells in the ileum, theoretically you should be able to increase the likelihood of improved hunger control. With that improved hunger control, you would be able to eat fewer calories.

A Clue from Gastric Bypass Surgery

The best example that such a scenario is possible was demonstrated with the advent of gastric bypass surgery first developed in the 1960s, initially to treat severe morbid obesity. In this type of surgery, you cut out much of the jejunum and rerouted the small intestine so that the majority of the dietary protein dumps directly into the ileum (the section of gut with the greatest concentration of L-cells). The result is the patient has a dramatic reduction in hunger with far fewer calories. In fact, the results are virtually immediate in giving the gastric bypass patient freedom from hunger. Today, gastric bypass surgery remains the best long-term treatment (although barbaric because you are cutting out normal tissue and potentially introducing a lifetime of malnutrition) that we have for the long-term treatment of both obesity and diabetes (3,4).

The Third Evolution of Protein: Zone Foods

Once the mechanism of gastric bypass surgery on hunger was understood to cause an increase in satiety hormones reaching the brain, I figured it should be possible to develop the third evolution of protein that would activate the L-cells in the gut to achieve the same goal. The problem was delivering more protein to lower part of the gut (the ileum) to generate similar hormonal responses generated by gastric bypass surgery. Based on drug delivery techniques I developed decades ago for reducing the toxicity of cancer drugs, lead to the development of the Zone Foods. The goal being to replicate similar hormonal responses to that of gastric bypass surgery for the long-term treatment of obesity and diabetes without the surgery. This technology allowed for the development of a wide number of unique satiety “drugs” ranging from breakfast cereals, pasta, pizza, tortillas, and even pastries.

The underlying cause of both obesity and diabetes is insulin resistance. To test the concept of Zone Foods in real life, we recently completed a placebo-controlled clinical study with obese subjects who had significant insulin resistance. The results were extraordinary (5). The subjects who consumed the Zone Foods made using this new technology saw a dramatic reduction of their insulin resistance compared to the control group who consumed essentially the same amount of protein and calories, but using traditional protein sources. In addition, they gained more muscle without increasing their levels of exercise.

With the advent of Zone Foods, an entirely new chapter of hunger control is possible using protein in which you have potentially changed the location of its absorption in the gut. This is the third evolution of protein. The more you incorporate Zone Foods into your diet as a replacement for animal protein, the greater the reduction of insulin resistance. This is the key for managing obesity and diabetes for a lifetime especially since you can do this using food people enjoy eating to ensure lifetime compliance. New call-to-action


  1. Wrangham R. Catching Fire: How Cooking Made Us Human. Basic Books. New York, NY (2009)
  1. Gilad Y, Oshlack A, Smyth GK, Speed TP, and White KP. “Expression profiling in primates reveals a rapid evolution of human transcription factors.” Nature 44:242-245 (2006)
  1. Brethauer SA, Aminian A, Romero-Talamás H, Batayyah E, Mackey J, Kennedy L, Kashyap SR, Kirwan JP, Rogula T, Kroh M, ChandB, and Schauer PR. “Can diabetes be surgically cured? long-term metabolic effects of bariatric surgery in obese patients with type 2 diabetes mellitus.” Ann Surg 258: 628–637 (2013)
  1. Chen Y, Corsino L, Shantavasinkul PC, Grant J, Portenier D, Ding L, and Torquati A. “Gastric bypass surgery leads to long-term remission or improvement of type 2 diabetes and significant decrease of microvascular and macrovascular complications.” Ann Surg 263:1138-1142 (2016).
  1. Johnson CS, Sears B, Perry M, and Knurick JR. “Use of novel high-protein functional food products as part of a calorie-restricted diet to reduce insulin resistance and increase lean body mass in adults: A randomized controlled trial.” Nutrients 9:1182 (2017)

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