Why Restrictive Diets Often Fail at Long-Term Weight Loss

People hoping to lose weight this year may feel drawn to a diet challenge as a way to kick-start their weight loss.

However, although short-term restrictive diets can seem like a useful way to reduce your waistline, psychology and physiology explain why they are difficult to maintain – and why they are unlikely to produce lasting weight loss.

Research suggests that as few as 20 percent of people who lose weight by dieting succeed in keeping it off in the long term.

Psychologists have spent decades investigating why diets fail so frequently.

Why restrictive diets trigger cravings

One explanation is that diets commonly impose rigid rules around food, such as cutting out foods you enjoy.

The difficulty is that foods people often want most – including chocolate, ice cream and crisps – stimulate the brain's reward system, creating positive feelings.

Removing these foods from your diet takes away the enjoyment they provide. In turn, this can prompt food cravings: a complex psychological response involving a powerful urge to eat a specific food, even if you are not hungry.

Cravings are often linked to mood and can become particularly strong when we are stressed. They may also be more intense in the late afternoon and evening, when tiredness leaves us with less willpower to resist them.

Food cravings may lead to overeating, particularly when you are attempting to diet. One review found that people who intentionally removed particular foods from their diet developed stronger cravings for the foods they were avoiding.

While the review's authors conclude that this response can be unlearned, it helps explain why even brief restrictive diets often fail. Crash diets may intensify food cravings, making goals harder to maintain – and potentially causing weight gain instead.

Repeatedly failing to diet can also damage self-efficacy, meaning our belief in our ability to succeed. This psychological resource is important when making changes that last.

Nutritionists likewise agree that short-term restrictive diets are not ideal for successful long-term weight loss.

Our appetite – how hungry we feel – and satiety – how long we remain full – are regulated by complex physiological signalling pathways that have an important role in weight loss.

When we adopt very low-calorie diets, the body responds by increasing appetite, decreasing satiety and even lowering energy expenditure, or the number of calories we burn.

It also offsets severe calorie cuts by sending more powerful hunger signals to the brain, which can encourage overeating.

Why rapid weight loss can lead to weight regain

These physiological reactions mean excessively restrictive diets may make losing weight more difficult – and can even result in regaining weight.

From an evolutionary viewpoint, these responses enabled our ancestors to survive periods of food scarcity. Today, however, they help explain why extreme calorie restriction so commonly results in weight regain. Research shows that people typically regain around 50 - 70 percent of the weight lost after dieting.

A further possible reason is that a falling number on the scales does not only reflect fat loss – muscle is lost too. This is significant because muscle makes a major contribution to resting energy expenditure, which forms part of metabolism. Research has also linked a reduction in muscle mass with weight regain.

Because rapid weight loss diets produce a substantial energy deficit and can provide less protein, they raise the risk of muscle loss. They also make it more likely that you will regain the weight lost during the diet.

The best strategies for weight loss

If you want to make a significant effort to lose weight, an "all-or-nothing" crash diet may not be the right choice. A more gradual and balanced method is much more likely to preserve muscle and support results that last longer.

Focus on nutrient quality, rather than calories

When it comes to healthy eating, the aim should not be to "diet". As we have seen, calorie restriction often has the opposite effect because the body and brain compensate with stronger hunger signals and food cravings. Rather than concentrating on foods to remove, consider what you could add to make meals more nutritious.

The foods we choose affect appetite and satiety signals, not merely the number of calories consumed. Protein, for instance, helps us feel full, while high-fibre carbohydrates are more satisfying than heavily processed refined alternatives.

Choose nutrient-dense foods. A good starting point is adding plenty of fibre to meals through wholegrains, pulses, lentils, beans, fruit and vegetables.

Research indicates that consuming more fibre as part of a balanced diet may also help you maintain a healthy body weight throughout your life.

Instead of making temporary changes in January, make small substitutions that you can sustain for the entire year.

Approach it like a health coach

Health psychologists have developed behaviour-change frameworks that are known to support longer-term changes in physical activity and eating habits. Health coaches generally use these evidence-based methods to help patients make lifestyle changes, but you can act as your own coach by using some of them yourself.

Examples include setting goals, creating an action plan, recognising barriers and working with a friend or partner.

In practical terms, this might involve setting a realistic incremental weekly weight-loss goal of around 0.5 to 1 kg, identifying anything that could obstruct your goals, exercising with a friend and monitoring your progress.

Quick-fix, low-calorie diet challenges may promise rapid results, but they seldom create enduring change. Using evidence-based guidance from psychology and nutrition can help you avoid the restrictive diet trap this January and make more sustainable, long-term lifestyle changes.

Chloe Casey, Lecturer in Nutrition and Behaviour, Bournemouth University and Sarah Hillier, Senior Lecturer in Nutrition, Bournemouth University

This article is republished from The Conversation under a Creative Commons licence. Read the original article.