The Hormones of Appetite

It is a pretty well established fact that the main reasons for weight gain are eating too much of the wrong foods and moving too little. However, the precise mechanisms that control appetite and weight are still being investigated.

Energy Intake vs Energy Expenditure

Taking in an adequate supply of energy from food relative to the amount of exercise you are doing is crucial for survival and reproduction. The balance between energy intake and energy expenditure is under the control of the brain and central nervous system. The mechanisms involved include a complex system of hormones and brain chemicals that control our food intake. Messages are constantly being sent between the brain and the gut as well as between the brain and other parts of the body such as the pancreas, the liver and adipose tissue (fat), This complex system can be disrupted by taking in too many of the wrong foods or not enough of the right foods over a sustained period of time (1).

There has been much research focusing on the hormones that control appetite. Two of these are ghrelin and leptin. These hormones act on parts of the brain that regulate the sensations of satiety or fullness when we eat. Ghrelin sends signals that tell you to eat while leptin sends signals to indicate that you are full. In other words too much ghrelin will make you eat more and not enough leptin will mean you won’t know when to stop eating.

The Problem with Low Calorie Diets

Research has found that obese individuals put on a low energy diet had significant reductions in leptin and increases in ghrelin compared to their baseline measurement at the start of the trial. There were also increases in subjective appetite. In other words, the reason that calorie cutting diets don’t work is that reducing calories weakens the leptin signals, which tell you when to stop eating, and strengthens ghrelin – the one telling you to eat more.

This explains why so many people who go on a low calorie diet pile the weight back on after the diet. The changes in the appetite regulating hormones that encourage weight gain continue for over a year after the dieting period (2).

Here are some tips for getting back in touch with your appetite control mechanisms:

• Avoid low calorie diets – as described above, these may lead to initial weight loss but will ultimately lead to weight gain.
• Listen to hunger and do not under-eat – ignoring hunger signals and not eating sufficient amounts to satisfy your hunger can lead to imbalances in the hormones that control appetite. When you do start to eat you may not know when to stop or you may reach for fatty or sugary foods as your body tries to re-coup the calories of which it is has been deprived.
• Avoid over-eating – there are many occasions when over-eating seems acceptable and is almost unavoidable. However, just because there is a lot of food available doesn’t mean you have to eat it all. There will be food available later so you don’t need to gorge yourself at this sitting. Eating until you are excessively full is another way of loosing touch with your appetite control mechanisms.
• Slow down – eating slowly is a good way of not over-eating as it gives your body a chance to register the signals regarding fullness.
• Chew thoroughly and savour each mouthful – chewing each mouthful until it is liquid before you swallow it will help you to slow down and will increase your enjoyment of the different flavours and textures in your food, whilst also improving the digestion and absorption of nutrients.
• You don’t have to eat everything on your plate – the amount of food on a plate is often arbitrary and may not relate to the amount of food you need. If you start to feel like you may be satisfied put down your knife and fork and let your food settle. You will probably find you have had enough and no longer need any more. There is no need to waste the food – put left overs in a covered container in the fridge for later.
• Use a smaller plate – if you find it impossible to leave food on your plate this is a good solution.
• Avoid sugar – whilst sugar consumption is associated with weight gain due, in part, to its effects on the hormones that are responsible for appetite and blood sugar control, honey does not seem have the same negative effects. Research shows that honey consumption actually delays the ghrelin response after meals (3), meaning that hunger will be delayed. Please note, that while honey is a better choice than refined sugar it should be consumed in moderation.
• Eat high water content foods – fruit, vegetables, well cooked whole grains and pulses all have a high water and fibre content meaning that they will fill you up. However, if you eat calorie rich and nutrient poor foods such as crisps, biscuits, cakes and pastries it’s easy to eat too many calories while not getting sufficient nutrients. Your body will feel under nourished and you will want to eat more.
• Develop other interests – if you are one of those people who thinks about food constantly then you will most likely be making yourself hungry even when you do not have a genuine physical need for food. Distract yourself by taking up exercise, doing voluntary work or starting a hobby.
• Beware using food as a stress reliever – find other ways of dealing with stress. Yoga, tai chi, meditation, breathing exercises, talking to friends or family or walking in nature are all good ways of managing the ups and downs of life.
• Relax before, during and after meals – take some deep inhalations and exhalations before you eat and give thanks for the food. Eat in a relaxed manner without distractions. Sit for a few minutes after meals rather than getting up and rushing around.
• Enjoy your food – food should be delicious. Healthy eating does not mean meals become a joyless chore. Experiment with different recipes, salad dressings and natural flavourings such as miso, tamari, whole grain mustard, ginger, herbs and spices to make all your food really tasty. See blog posts Step out of the Menu Rut and How Umami Affects Food Choices for more information and ideas.
• Make sure you are not dehydrated before you eat – this may lead to eating when you are not really hungry and eating too much. Ideally have a large drink of water or herbal tea 20 minutes before meals.
• Get off your butt – research shows that sitting for long periods of time in which there is very little energy expenditure does not reduce appetite indicating that prolonged sitting may promote excessive energy intake and weight gain (4).
• Exercise – exercise tends to improve appetite control, partly due to its beneficial effects on blood sugar control. Having stable blood sugar tends to make it easier to tune into your true hunger and can lead to better food choices.
• Sleep – short sleep duration and reduced sleep quality are both associated with disrupted appetite control that may result in increased food intake and snacking (5). Get into good sleep habits – have a relaxing bed time routine and go to bed and get up at the same time each day.

References

1. 1. Faulconbridge LF, Hayes MR.  Regulation of energy balance and body weight by the brain: a distributed system prone to disruption. Psychiatr Clin North Am. 2011 Dec;34(4):733-45.
2. 2. Sumithran P, Prendergast LA, Delbridge E, Purcell E et al. Long-term persistence of hormonal adaptations to weight loss. N Engl J Med. 2011 Oct 27;365(17):1597-604.

3. 3. Larson-Meyer DE,WillisKS,WillisLM,AustinKJ,HartAMetEffect of honey versus sucrose on appetite, appetite-regulating hormones, and postmeal thermogenesis. JAmCollNutr. 2010 Oct;29(5):482-93.

1. 4. Granados K, Stephens BR, Malin SK, Zderic TW, Hamilton MT, Braun B. Appetite regulation in response to sitting and energy imbalance. Appl. Physiol. Nutr Med. 2012 Apr;37(2):323-33.

5. 5. Gonnissen HK, Hursel R, Rutters F, Martens EA, Westerterp-Plantenga Effects of sleep fragmentation on appetite and related hormone concentrations over 24h in healthy men. Br J Nutr. 2012 Jun 8:1-9