In the land of weight loss, satiety is king.
“Satiety” is science-talk for feeling full. Satiety is caused by eating food. Information about the amount of food in your GI tract—like how much it’s stretching your stomach (“gastric distension”)—is communicated to your brainstem and hypothalamus by peptide signals with arbitrary names like cholecystokinin, glucagon-like peptide 1, and peptide YY.142,143
If these signals are strong enough, voila! Your appetite is curbed.
Satiety is critical to weight loss because we’re always getting hungry, we’re always eating, and we’re always getting full—one of the great circles of life.
And when it comes to satiety, wait for it…foods are not equal. Per calorie, some foods are far more filling than others.144,145,146,147
It’s hard to overstate the importance of this.
Just for the sake of argument, let’s say you’re not an ascetic monk who chooses to live with continual hunger pangs. In that case, you will generally, more or less, most of the time, often enough to count…eat until you feel somewhat full.
And if you consistently eat foods on the less-filling end of the spectrum, you’ll have to eat more total calories to feel full.
So you will eat more total calories.
(Because you’re not an ascetic monk who chooses to live with continual hunger pangs.)
And we all know what happens when you consistently eat more calories. You gain fat. And if you give it enough time, unless you’re a genetic luck-pot, you get fat.
While some people are genetically disposed to be fat, most people get fat because their regular diets contain less-filling foods.
People can get skinny by removing these less-filling foods from their regular diets, and replacing them with more-filling foods (that still taste good; no ascetic monking required).
The key is to base your diet on filling foods.
But what foods are more filling, and which are less filling?
Where is this spectrum of filling-ness?
It’s very simple. You don’t have to worry about any details.
Just think of one, all-important, neon-bright dividing line:
processed foods vs. whole foods
Processed foods (definition to come) are generally much less filling than whole foods.148,149 Because processed foods are less filling, when people have unlimited access to processed foods (like most of us do) they tend to eat more total calories.150,151,152
Food processing is a science, an art, and an evolutionary novelty. It creates uber delicious foods that are aliens to our body’s satiety system, which evolved regulating whole-food diets.
For all its alleged complexity, the obesity epidemic is very simple. People eat too much processed food. A 2015 study found that 77% of the food Americans buy is processed, and that 61% of it is “highly processed.” 153
This is why 71% of us are overweight.154
And in the cause lies the cure. Get in the habit of eliminating processed food from your regular diet.
(Your regular diet is the diet you eat most days of the week.)
But what exactly is “processed food,” aside from the obvious junk foods? Great question. The term processed food isn’t in the dictionary, so here’s a useful, practical definition to bring to the supermarket:
processed food n : a food with an ingredients list longer than one item
Let’s see what makes processed food so bad.
142. Chambers et al., “Integration of Satiety Signals by the Central Nervous System,” Current Biology 23, no. 9 (2013): R379-R388.
143. Guyenet, S., and Schwartz, M., “Regulation of Food Intake, Energy Balance, and Body Fat Mass: Implications for the Pathogenesis and Treatment of Obesity,” The Journal of Clinical Endocrinology and Metabolism 97, no. 3 (2012): 745-755.
144. Holt et al., “A Satiety Index of Common Foods,” European Journal of Clinical Nutrition 49, no. 9 (1996): 675-690.
145. Geliebter et al., “Effects of Oatmeal and Corn Flakes Cereal Breakfasts on Satiety, Gastric Emptying, Glucose, and Appetite-Related Hormones,” Annals of Nutrition & Metabolism 66, no. 2-3 (2015): 93-103.
146. Soto et al., “The Form of Energy-Containing Food Alters Satiety and fMRI Brain Responses in Humans,” The Journal of the Federation of American Societies for Experimental Biology 29, no. 1 (2015): Supplement 983.1
147. Bligh et al., “Plant-Rich Mixed Meals Based on Paleolithic Diet Principles Have a Dramatic Impact on Incretin, Peptide YY and Satiety Response, but Show Little Effect on Glucose and Insulin Homeostasis: An Acute Effects Randomised Study,” British Journal of Nutrition 113, no. 4 (2015): 574-84.
148. Holt et al., “A Satiety Index of Common Foods,” European Journal of Clinical Nutrition 49, no. 9 (1996): 675-690.
149. Duncan et al., “The Effects of High and Low Energy Density Diets on Satiety, Energy Intake, and Eating Time of Obese and Nonobese Subjects,” American Journal of Clinical Nutrition 37, no. 5 (1983): 763-7.
150. Risling et al., “Food Intake Measured by an Automated Food-Selection System: Relationship to Energy Expenditure,” American Journal of Clinical Nutrition 55, no. 2 (1992): 343-9.
151. Larson et al., “Ad Libitum Food Intake on a ‘Cafeteria Diet’ in Native American Women: Relations with Body Composition and 24-H Energy Expenditure,” American Journal of Clinical Nutrition 62, no. 5 (1995): 911- 7.
152. Larson et al., “Spontaneous Overfeeding with a ‘Cafeteria Diet’ in Men: Effects on 24-hour Energy Expenditure and Substrate Oxidation,” International Journal of Obesity and Related Metabolic Disorders 19, no. 5 (1995): 331-7.
153. Poti et al., “Is the Degree of Food Processing and Convenience Linked with the Nutritional Quality of Foods Purchased by US Households?” American Journal of Clinical Nutrition (2015): doi: 10.3945/ajcn.114.100925
154. “Obesity and Overweight,” Centers for Disease Control and Prevention. https://www.cdc.gov/nchs/fastats/obesity-overweight.htm