Science of Fullness

Being hungry and having a craving are not the same thing, but sometimes it’s hard to tell them apart. Understanding your body’s natural cues for hunger and fullness can help you outsmart cravings and stay on track to reach your goals.

Hunger vs. Cravings

Hunger is the sensation we experience when we are low on nutrients and energy. It’s our body’s way of signaling that we need to find something to eat — think of a rumbling stomach or a feeling of weakness.

Cravings come from the brain. They can be signaled by a variety of cues: a yummy smell, a late-night sweet tooth, boredom, a commercial, or even emotions like stress and sadness.

A good way to tell if you are truly hungry is to ask yourself if any nourishing food will satisfy you. If the answer is yes, this is hunger. If only one type of food will do the trick, this is likely just a craving.

What Is Going On in Your Body?

Many of us associate hunger with a rumbling stomach or the amount of time that’s passed since our last meal, but the body has a complex process to regulate hunger and fullness involving hormones and a close link between the brain and stomach.

If it has been a few hours since your last meal or snack, your blood sugar and insulin levels will start to drop. For some, this translates to feeling irritable or “hangry,” while others experience low energy levels or headaches.

Internally, this drop in blood sugar signals the brain to release the hormone ghrelin (1). Ghrelin lets your body know that it has used up the readily available fuel and that it’s time for a refill. Ghrelin is often thought of as the hunger hormone because it stimulates the processes associated with hunger in the body.

Once food starts filling your stomach, your stomach cues the brain to slow the release of ghrelin and turn up the release of peptide YY (PYY). This hormone promotes a feeling of fullness and satisfaction after a meal, letting you know your body is no longer in need of food (1).

Outsmart Cravings

Recognizing the difference between hunger and cravings can help you stay on track and eat when your body needs fuel instead of eating for other reasons. Here are a few tips to help you listen to your body, feel your best, and achieve your health goals.

Space out meals and snacks to avoid feeling starved

Providing your body with the right nourishment every few hours can help stabilize blood sugar levels and keep your hunger hormones in check. For most, skipping meals and snacks can result in feelings of extreme hunger, leading you to overeat later or cave in to cravings.

Load up on fiber and protein to help you feel satisfied longer

Whether you are snacking or enjoying a meal, make sure it’s packed with protein, fiber, or ideally both. Foods high in protein and fiber help to slow digestion, helping you feel satisfied longer.

Practice mindfulness when it comes to when and what you eat

Mindfulness may seem like the latest trend, but it’s really about taking a moment to check in with your body and see how you are feeling. Before sitting down for a meal, ask yourself if you feel hungry or if you are just eating because it’s lunchtime.

Give intermittent fasting a try for an appetite reset

The science behind intermittent fasting has guided Isagenix Cleanse Days from the start. One of the exciting areas of research surrounding intermittent fasting is the common theme of participants feeling less hungry following a day of intentional fasting. Researchers at the University of Illinois at Chicago have found that regular intermittent fasting days (like Cleanse Days) may help reset your appetite (2)!


  1. Amin T, Mercer JG. Hunger and Satiety Mechanisms and Their Potential Exploitation in the Regulation of Food Intake. Curr Obes Rep. 2016 Mar;5(1):106-12. doi: 10.1007/s13679-015-0184-5.
  2. Hoddy KK, Gibbons C, Kroeger CM, Trepanowski JF, Barnosky A, Bhutani S, Gabel K, Finlayson G, Varady KA. Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting. Clin Nutr. 2016 Dec;35(6):1380-1385. doi: 10.1016/j.clnu.2016.03.011.

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