Gluttony occurs when we over-consume to the point of extravagance or waste. Historically gluttony was seen as a major sin (it distracted people from their religious observances), but today it’s almost as if gluttony is expected in Western culture. We demonstrate our wealth by showing an overabundance of “stuff.”

Companies encourage this overabundance by making us feel like we deserve to be rewarded and by escalating our level of commitment beyond what we first intended, drawing us in from early engagement through to full-on compliance. Sites also make us fearful of missing out—scarcity, exclusivity, and loss aversion play on the fears behind gluttony.

Make customers work for a reward: People put more value on a reward that is not available to everyone.

Consider a small reward rather than a big one: Users will be forced to create justifications, which increase the perceived value of the reward.

Hide the math: People don’t like doing sums, and so if you show them answers rather than the workings, they’ll be inclined to believe you—even if the answers are only partial.

Show the problems: Mention weaknesses before customers find out. They’ll trust you more.

Foot-in-the-door: Gain commitment to a small thing to convince about a big thing.

Door-in-the-face: Ask for a big thing, expecting to be turned down. Then ask for a small thing immediately afterward. Guilt at turning you down makes users more likely to agree to the small thing.

Present hard decisions only after investment: Ensure that users are hooked before you ask them to give you “valuable” information or perform hard tasks. Better to give something away free than lose the future value.

Tom Sawyer Effect; Scarcity breeds desire: “In order to make a man or a boy covet a thing, it is only necessary to make the thing difficult to attain.”

Instill doubt to prevent cancellations: If customers want to cancel, instill doubt by tapping into loss aversion.

Impatience leads to compliance: Put a time constraint on a task and then offer to help users through it.

We are easily fooled into gluttony. Just having healthy options available on menus or among the selections from a vending machine is sometimes enough to make our brains think we’ve satisfied our health and nutrition goals, and therefore allows us to choose less honorable options.

The average restaurant meal in the United States is four times larger now than it was in the 1950s, yet we might still be fitting into the same size clothes as we always have. That’s because what was a size 14 dress in the 1970s is not the same size garment today. The Economist found that women’s size 14 (UK) clothes are about 3 inches larger in the hips than they were in 1970, thus about the equivalent of a 1970s size 18. Men’s clothes also lie: a recent Esquire investigation found that some brands of 36-inch trousers actually measured as much as 41 inches.