No one can eat just one! But why?

Why do we enjoy eating junk food so much? What makes them so tasty? The pleasure one derives from food is dependent on the food sensation (taste, smell and texture) plus the calories (protein, carbs and fat).

Taste Hedonics: Food must contain correct amounts of salt, sugar, MSG, and flavor-active compounds for it to be tasty. Taste is a major driver of ingestion and pleasure in food, but it only accounts for less than 10 percent of all the sensation from the mouth to the brain.

Dynamic Contrast: We prefer food with sensory contrasts, light and dark, sweet and salty, rapid meltdown in the mouth, crunchy with silky, and so on. Temperature changes in the mouth can be highly pleasurable, explains the popularity of gulab jamuns with ice cream or the lava cake with ice cream providing a flood of textures, taste and temperature.

Energy Density: Humans crave the calorically dense foods when we see or sense them, or as we call them, fast food. Energy-dense foods are tasty but not filling, whereas foods with low energy density are more filling but less tasty. Energy density is a number from 0–9, and it is calculated by dividing calories (kcals) by the gram weight of a food. Most vegetables are near 1, meats climb to 2–3, fast and junk foods hover around 4.0–5.0, and butter is around 7.2. 

Vanishing Caloric Density:  We tend to like foods with high oral impact, plenty of taste and dynamic contrast, but with low satiating ability or immediate gastric feedback. For example, cotton candy, popcorn, meringues etc. Foods like popcorn that rapidly melt in your mouth signal brain that the food ingested in lower in calories than it really is, this results in you eating more than your realise.

Sensory-Specific Satiety: Junk Foods are designed to overcome sensory-specific satiety, which refers to a temporary decline in pleasure derived from consuming a certain food compared to other unconsumed foods. For example, after having a big slice of cake, the pleasure you would derive from the second slice would be obviously lower. In a way it is similar to the concept of diminishing marginal utility. This decline in pleasure is the body's way of encouraging the intake of a wide variety of foods. But high energy dense food with vanishing caloric density, like popcorn which melts in the mouth can be more rewarding, reduce satiety and cause overeating.

Conditioning after eating: Consuming the macronutrients (fat, protein, and carbohydrate) quickly conditions human to prefer the taste of that food. Sweet, fatty foods or high calorie foods condition easily. Junk food, unusually rich in components like salt, fat, sugar, and umami, with high caloric density, readily create strong food preferences. 

Emulsion Theory: Taste buds like emulsions, especially salt-fat or sugar-fat combinations. Many of our tastiest foods are in liquid or solid phase emulsions, like butter, chocolate, salad dressings, ice cream, hollandaise sauce, mayonnaise, or crème. The making of an emulsion concentrates the salt, sugar, and MSG into the water phase. Ice cream is a frozen emulsified “foam” that concentrates the sugar in the water phase, enhancing the perception of sweetness, while the butter enhances the taste of salt.

Salivation Response: We prefer foods that are moist or evoke saliva during the chewing process. If you add fat to a dry food (potato chips are 50 percent fat calories), you have additional oral lubrication—the perfect “salivation” food. Thin potato chips have a texture that melts down very quickly and stimulates salivary flow. The tastiest foods should evoke saliva or at least provide lubrication and moistness.

With the brain having a predisposition to high energy density food, getting tempted by taste, aroma and texture, how do we avoid junk food craving?

The brain calculates the pleasure from eating and digesting the food. The goal of the brain, gut, and fat cell is to maximize the pleasure extracted from the environment, both in food sensation and macronutrient content. If a food is lowered in calories for health reasons, the gut has the ability to sense this, and the food will become less palatable over time. To compensate for the lower calories, one must add additional sensation, for e.g., greater dynamic contrast, aroma, etc. Lowering calories but not adding any sensation is unlikely to cause acceptance. Add some novelty and variety to satisfy your brain, for example dip a crunchy carrot in some creamy hummus, instead of just having a carrot by itself or maybe add some aromatic spices to flavor your food.

To read more: https://www.amazon.in/Why-Humans-Like-Junk-Food/dp/059541429X