Your body doesn’t know when you’ve overeaten, but exercise can help
Losing weight is often at the forefront of many people’s minds at the start of the year. But if weight loss was your goal for 2019, chances are that by now, you’ve probably already experienced some challenges.
That’s because sticking to a strict calorie controlled diet is not an easy task in modern environments – where tasty and high energy foods are attractive and easily available. Dieting is also made particularly difficult by our body’s rapid response to decreases in food intake but opposing lack of response to overeating. This will be a familiar experience for many who have experienced almost immediate increases in hunger when dieting.
Most people will also have experienced how easy it is to overeat during holiday periods or other occasions. A main course meal at a UK full service restaurant, for example, is likely to contain more than half of the calories required for an entire day.
Overeating not detected
Our recent research has shown that overeating is poorly detected in humans, even when energy intake is increased to provide an excess of more than 1,000 calories per day.
In this study, overeating with 150% of the required daily calories did not change the appetite of participants. We tested for this by looking at appetite ratings and levels of specific hormones known to regulate appetite, as well as checking the food intake of participants during the next day.
Our findings showed how the body fails to adjust to account for these additional calories. This makes sense from an evolutionary perspective because in environments with limited access to food, overeating when food was available to our ancestors would increase their chances of survival by keeping them fuelled until food was available again.
This shows that being aware of calorie intakes is important because short periods of accidental overeating can be sufficient to cause weight gain or impair weight loss. Indeed, some evidence suggests that increases in body weight during the festive period are maintained throughout the rest of the year. And may also be responsible for incremental annual increases in body weight. Similarly, overeating on a weekend can easily cancel out a strict diet that is maintained on weekdays.
But understanding how easy it is to overeat does not mean that weight loss can’t be achieved. In fact, knowing this can help with weight loss – by being more aware of dietary choices.
Don’t forget exercise
Despite our body’s bias for weight gain, correct diet and lifestyle changes will produce and maintain weight loss if this is the desired aim.
Exercise may often be overlooked as people seek “the best diet for weight loss”. But getting active still remains important if you want to lose weight – and especially for maintaining weight loss over prolonged periods of time.
Exercise can complement dietary changes and help to minimise the increases in hunger experienced from dieting alone. This is because exercise does not cause an increase in hunger to the same extent as dieting, despite also creating an energy deficit for weight loss.
In fact, hunger is reduced when exercising intensely, which may help to stave off hunger pangs while increasing the energy deficit.
The importance of exercise for maintaining weight loss was also recently highlighted with participants from the US televised weight loss competition, The Biggest Loser. The tracking of participants for six years after the show revealed that the people who maintained their weight loss had increased their physical activity by 160%. Whereas those who regained their lost weight had only increased physical activity by 34%.
Regardless of which dieting approach you choose, it is likely you will need a degree of flexibility – as most diets will require some compromise.
Perhaps, for example, you are invited to attend a meal at a restaurant for a special occasion or there is a holiday celebration involving additional eating. Being aware that your body is not likely to respond to the increased calorie intake means that you can adjust your behaviour to avoid or compensate for any overeating, for example by being more mindful of food choices in the days before or after an occasion, or increasing your exercise levels to counter any excesses.
What all this shows is that ultimately we should not rely on feedback signals from our body to detect levels of calorie intakes. Instead, conscious monitoring of diet and lifestyle behaviours is more than sufficient to counter our body’s natural bias for weight gain. And by appreciating this need for conscious monitoring, it may help you to achieve any desired weight loss goals over the year ahead.
Reader in Nutrition and Metabolism,
Leeds Beckett University
* Published in print edition on 15 February 2019