Hunger is painful and uncomfortable. Diets which restrict food and calorie intake often fail because we become overwhelmed by feelings of hunger. Sensations of hunger are natural signals produced by hormones, but sometimes the signals don’t work properly and we feel hungry all the time. Taming hunger is the key to successful weight loss. Here we summarise what the science tells us about hunger and show how low-carb eating frees us from the tyranny of hunger!
1. The Minnesota Starvation Experiment - the impact of hunger
Hunger makes us uncomfortable and distressed, and excess hunger frequently leads to failure in weight loss. The basis of many diets is to reduce intake of calories – conventional weight loss theory is to eat less and exercise more. However, expecting people to tolerate hunger over a weeks or months is unrealistic and cruel.
The long-term effects of hunger were studied in an experiment undertaken in 1944 by Ancel Keys (1950) called the Minnesota Starvation Experiment. One hundred American conscientious objectors were recruited to assess the impact of starvation on human health. One phase of the study required 12 weeks of semi-starvation – with food intake reduced to 1560 calories/day of foods, mainly carbohydrates, such as potatoes, bread, turnips, and macaroni. Apart from the negative physical impact on the men, the psychological impact of this diet was extreme, and the study concluded that prolonged semi-starvation produced severe emotional distress, including depression, hysteria and even self-mutilation.
2. So what is hunger and how is it regulated?
The human body has a number of ways to maintain a healthy weight, ways that encourage us to eat when we need to and stop when we don’t. Two types of signals which affect our intake of food - the signal to start eating and the signal to stop eating:
Appetite and hunger – signals that lead us to seek out food
Satiety – the feeling of fullness that we usually get after eating
Several hormones send messages to the brain which lead to feelings of hunger and satiety. In response to food or lack of food, hormones signal hunger or satiety in the hypothalamus, the control centre for appetite in the brain. Some of the main hormones involved are:
Ghrelin – produced in the upper part of the stomach promoting feelings of hunger when we are deprived of food.
Peptide -YY (PYY) – produced by cells in the small intestine in response to food entering the small bowel from the stomach. It acts on the brain to produce feelings of satiety (fullness).
Leptin - produced by our fat cells and providing messages to the brain’s weight control centre about the amount of fat being carried on the body. Leptin levels should be high when we are carrying a lot of fat and low when we are slim. If fat reserves are depleted, leptin will direct the brain to become hungry and to eat. If fat reserves are plentiful, leptin will take away hunger.
When things are working normally, leptin helps the body maintain its natural set-point weight, so that we don’t have to think about maintaining our normal weight – it happens naturally.
3. So, what can go wrong with our hunger and satiety signals?
a). Calorie-restricted diets
Research shows that calorie-restricting diets have a negative impact on our normal hunger and satiety signalling. One study found ghrelin (hunger hormone) levels were elevated and PYY (satiety hormones) signalling was significantly lower in people after they had been on a calorie-restricted diet (Sumithran et al, 2011). So unfortunately, calorie-restricted dieting can increase feelings of hunger and reduce satiety contributing to weight gain following a diet.
b). Leptin Resistance
The leptin signals from fat cells in overweight people may become disturbed so the brain appears unaware of the fat reserves and senses a much lower level of leptin, which it interprets as starvation. This is known as leptin resistance and leads to increased hunger and often results in further weight gain. (Jenkinson, 2020).
This disruption to the leptin signal may be caused by raised insulin levels in the body, as insulin may prevent the leptin message from being received by the brain. High circulating insulin can therefore lead to leptin resistance.
4. How the food we eat impacts on our hunger?
Our appetite is also affected by the foods we eat.
Carbohydrates
Eating a diet high in sugars and carbohydrates can increase hunger. If you eat a high carbohydrate meal your blood glucose is likely to rise quickly first, and then fall sharply. This dip in blood sugar leaves you feeling tired and hungry – and we call these glycaemic highs and lows the ‘blood sugar roller-coaster’.
Research shows that these spikes and dips in glucose increase hunger and lead to greater food intake at the next meal. (Chandler-Laney 2014).
A bigger blood glucose dip after a meal leads to an earlier return of appetite
A study undertaken by Kings College Hospital in London recently found that those people who experience the lowest dips in blood sugar following a spike also became hungrier sooner than those who don’t experience such a low dip (Wyatt, 2021).
In the long term, eating a high carbohydrate diet can lead to raised insulin levels, and as described earlier, high insulin levels obstruct leptin signals from the fat cells leading to leptin resistance. Leptin resistance leads greater hunger and weight gain.
Protein
Studies show that eating more protein in your diet increases feelings of fullness, lowers hunger hormones and may help you to eat less at your next meal. One study found that those who ate eggs rather than cereal for breakfast had increased feelings of fullness after the meal and reduced hunger hormones (Bayhem et al 2014). These benefits are not limited to animal proteins, as vegetable proteins are also found to increase satiety (Neilsen, 2018).
Fats and fibre
It is sometimes suggested that by adding bulk to our diets, fibre helps to reduce hunger. However other theories suggest that what may be more important is the brain sensing whether there is sufficient energy available (Bickman, 2020) One study assessed hunger in those using intravenous (IV) feeding, in which no food enters the stomach. They found that if the infusion contained just glucose the person would feel hungry, whereas, when the infusion also contained some fat, feelings of hunger disappeared (McCutcheon, NB,1989)
Fats are the one macronutrient that don’t raise insulin levels and eating healthy fats can also help to keep hunger at bay longer.
5. Managing hunger when you’re trying to lose weight
If you can't free yourself from the tyranny of hunger when you're trying to lose weight, it is very likely that your diet will fail. Hunger is just too difficult to live with. As the famous nutritionist, John Yudkin said:
6. Our recommendations for managing hunger
Based on the science above, our recommendations for reducing hunger when you’re trying to lose weight are as follows:
7. It works - low-carb reduces hunger!
People who have been on our on-line low-carb weight loss programme frequently tell us that they are no longer bothered by hunger, they are able to go for much longer between meals and do not feel uncomfortable doing this. We usually suggest using time restricted eating, and many people move to eating just two meals a day – but do this because they are no longer suffering from hunger. Here are some quotes from participants from our Programmes:
“I am no longer feeling hungry and am eating significantly smaller portions”
“I barely felt hungry yesterday…it’s a wonderful contrast to my carb days when sometimes, no matter how much I ate, I didn’t feel full and the cravings were voracious”
“It’s so good not to be controlled by food”
8. To wrap up
Hunger can really get in the way when you're wanting to lose weight, and people who have been yo-yo dieters may experience disruption to their normal hormonal signals that govern hunger and satiety, leading to greater levels of hunger and discomfort. By choosing a low carbohydrate way of eating, with plenty of protein and healthy fats, it is possible to conquer the tyranny of hunger and lose weight more easily.
References
Bayham et al, 2014 ‘ A randomised trial to manipulate the quality instead of quantity of dietary proteins to influence the markers of satiety’. Journal of Diabetes and its complications’ Vol 28, issue 4. Pages 547-552
Bickman, Ben, 2020, Why we get sick. BenBella Books, Dallas.
Chandler-Laney, Paula C et al. 2014. “Return of hunger following a relatively high carbohydrate breakfast is associated with earlier recorded glucose peak and nadir.” Appetite vol. 80: 236-41. doi:10.1016/j.appet.2014.04.031
Jenkinson, A. ‘Why we eat (too much): The new science of appetite. Penguin Life.
Keys, A., Brozek, J., Henschel, A., Mickelsen, O., & Taylor, H. L., The Biology of Human Starvation (2 volumes), University of Minnesota Press, 1950
McCutcheon, NB and Tennissen 1989‘ Hunger and appetitive factors during total parenteral nutrition. Appetite 13. (2): p129-41
Nielsen LV et al, 2018. ‘Protein from Meat or Vegetable Sources in Meals Matched for Fiber Content has Similar Effects on Subjective Appetite Sensations and Energy Intake-A Randomized Acute Cross-Over Meal Test Study. Nutrients. Jan 16;10(1):96. doi: 10.3390/nu10010096. PMID: 29337861; PMCID: PMC5793324.
Sumithran et al. (2011). Long-term persistence of hormonal adaptions to weight loss. N Eng J Med, 346(21), May, 1623-30
Wyatt, P et al 2021. Postprandial glycaemic dips predict appetite and energy intake in healthy individuals. Nature Metabolism DOI:10.1038/s42255-02100383-x
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