The differences between us change everything, from how we digest food to how we recover from exercise. In "You Are Not Normal: Here's Why", I discussed how individual differences affect how well a training plan works. A program tailored to your strengths and weaknesses is what will work best for you. This time, we’re going to look at how nutrition changes for each of us, and how we can use this information to build a tailored diet plan. So let’s take look at a few individual differences that affect how we digest food.


Each body is unique and nutrition plans must be customized.


The Role of Hormones

A study in Cell looked at blood sugar levels after a meal. Glycemic index (GI) is used to rank foods based on how they affect blood sugar level. The researchers found that GI varied from person to person, suggesting each individual had a different reaction to carbohydrates. The research team therefore advocated a person-specific approach to nutrition.


Breaking Muscle Shop

Additionally, in the past twenty years scientists have learned much more about how hormones affect hunger. The hormone leptin is released from your fat cells and provides feedback on how many calories you are ingesting. Without going into too much detail, leptin inhibits neuropeptide Y, which sends a signal when we are hungry.


Based on this knowledge, you might think if we increased leptin in the body, we would feel fuller and eat less, but it’s not so simple. Think of this like a stereo with the volume cranked up. People who are overweight are unable to hear changes in the volume because the stereo is already so loud.


Another hormone called ghrelin signals to our body that we are hungry, and is responsible for the growling in our stomachs. Each of us has varying amounts of leptin, ghrelin, and neuropeptide Y, so we will each be more or less sensitive to their presence. These hormone levels also fluctuate. Here are just a few factors that lead to changes in levels:


  • Sleep: Lack of sleep tends to lower leptin and increase ghrelin. It is probably one of the reasons you might be hungrier after a few nights of less sleep.
  • Meal Frequency: Intermittent fasting tends to reset sensitivity to leptin.
  • Calorie Intake: Low-calorie diets tend to decrease leptin and increase ghrelin, which often leads to overeating after the diet is finished.


The Role of Gut Bacteria and Enzymes

You have an enzyme called amylase in your mouth that breaks down starch into sugar. Your genetic makeup changes how much amylase you produce. Researchers found that people with less amylase had increased blood sugar response. This means our genetics change how we digest starch, even at the onset of digestion.


"As you build your individualised nutrition plan, remember that systems interact, and your digestive system is as unique as you are."

The bacteria in our intestines also impact digestion. In recent research in Science, researchers studied identical twins. One twin was lean and the other obese. The scientists implanted the subjects’ gut bacteria into mice. The mice who received the lean person’s bacteria tended to be leaner. The other mice took on the obese twin’s shape. It seems the different gut bacteria changed how food was processed and stored in the body.


Further research suggests introducing specific varieties of gut bacteria can lead to weight loss. Additionally, people with more diverse types of gut bacteria tend to be leaner.


Putting the Theory Into Practice

So what should you do now?  My suggestion is to take a scientific approach to your diet.


  1. Experiment by changing one variable at a time to see how it affects you. Some changes might take weeks or months to take effect. It can take weeks for your gut microflora to transition from a carnivore diet to a vegetarian diet. Give yourself time to assess whether it worked or not.
  2. Reflect on which diets have worked well for you in the past. Your body has changed since you last tried that diet, but it might be a good place to start your research.
  3. Keep track of your changes. It is important to keep note of your results. I would suggest writing down weight, body fat percentage, psychological state, and side effects, along with your food diary. It will allow you to look back and determine whether your intervention worked.


Here are some items you might want to test out in these diet experiments:


  1. Eat less processed food. Foods with high levels of chemicals tend to harm gut bacteria and change our systems.
  2. Eat more pesticide-free vegetables. Plant-based products tend to provide nutrients that help your good gut bacteria grow. You may even want a bit of dirt on your vegetables, as soil-based organisms add to your gut bacteria diversity.
  3. Avoid antibiotics if you can. Antibiotics can affect your gut bacteria for up to one year. If you do need antibiotics, use fermented foods or probiotics to regrow the healthy gut bacteria.


Tailor Your Nutrition to You

Individual physiological differences play an important role in how well diets and training programs work. Basic training programs like Easy Strength and Simple and Sinister will work for the majority of people.


Similarly, basic diets might work for many people who are overweight. But as you approach your goal physique, your nutrition needs to be tailored to you. Someone else’s diet might not be the best solution. As you build your individualised nutrition plan, remember that systems interact, and your digestive system is as unique as you are.


More Like This:



1. Mandel, AL., Breslin, PAS., "High Endogenous Salivary Amylase Activity Is Associated with Improved Glycemic Homeostasis Following Starch Ingestion in Adults," The Journal of Nutrition (2012): 142 (5): 853–58.

2. Perry, GH., Dominy, NJ, et al., “Diet and the Evolution of Human Amylase Gene Copy Number Variation," Nature Genetics (2007) 39 (10): 1256–60.

3. Ridaura, V. K., Faith, J. J., Rey, F. E., Cheng, J., Duncan, A. E., Kau, A. L., Gordon, J. I., "Cultured gut microbiota from twins discordant for obesity modulate adiposity and metabolic phenotypes in mice," Science 2013 (New York, N.Y.), 341(6150). 

4. Sanchez, M., Darimont, C., Drapeau, V., Emady-Azar, S., Lepage, M., Rezzonico, E., Tremblay, A., "Effect of Lactobacillus rhamnosus CGMCC1.3724 supplementation on weight loss and maintenance in obese men and women," The British Journal of Nutrition (2013): 111(8), 1507–1519.

5. Zeevi, D., Korem, T., Zmora, N., Israeli, D., Rothschild, D., Weinberger, A., Segal, E., "Personalized Nutrition by Prediction of Glycemic Responses," Cell (2013), 163(5), 1079–1094.

6. Zhang, F., Gu, W. et al., "Copy Number Variation in Human Health, Disease, and Evolution," Annual Review of Genomics and Human Genetics (2009) 10: 451–81.


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