Why Diets Don't Work

Diets come in all shapes and sizes.

A ‘diet’ is a restrictive eating program used temporarily to lose weight. Diets are often gimmicky or have a certain theme such as the elimination of particular food groups or assigning points to foods. Some diets can be nonsensical, unscientific and downright dangerous – detoxes or juice cleanses anyone? *facepalm. Yes, these diets are restrictive, yes they may produce short term results, but why don’t they work long term?

We see so many clients with a history of yo-yo dieting. They’ve tried everything! Only to fall off the bandwagon, gaining more weight than they started with in the first place! It’s a shame they only come to see a Dietitian AFTER years of trying and failing at all of these programs…

Weight loss is based on the first law of thermodynamics:

“Energy cannot be created nor destroyed, but rather transformed from one state to another”

More affectionately rephrased as “calories in, calories out”. This, in theory, is true. When we consistently consume less energy than our body uses each day, weight loss follows. 

So why don’t diets work?

The human body is smart. It thrives on balance or homeostasis. Our body has inbuilt appetite and weight regulating systems which constantly strive to restore the balance.

The role of hormones in hunger

There are two hormones responsible for regulating our appetite: ghrelin and leptin.

Ghrelin is our appetite stimulating hormone; it is released into the stomach and sends hunger signals to the brain to produce ‘hunger pangs’.

Leptin is our appetite suppressing hormone, it is released by our fat cells after eating to send the signal that we’re full.

When we restrict our intake to lose weight, leptin levels plummet and ghrelin levels rise meaning our appetite soars. You’re up against strong feelings of hunger and it can become very difficult to resist extra snacks (or meals). Especially if you’re constantly thinking about what you can’t eat.

The role of metabolism

Our metabolism is clever and highly adaptable. It will respond to how much energy (calories or kilojoules) we consume. When our energy intake is high, the speed of our metabolism increases to ‘keep up’ with its energy workload. When our energy intake is reduced – our metabolism slows. One of the major reasons why metabolism slows relates to the effects of dieting on our body composition…

Losing weight on the scale doesn’t mean you’re only losing fat

Our body relies on energy from the macronutrients in our food (carbohydrates, proteins and fats) to perform lots of everyday body functions such as breathing and digesting. Stripping kilojoules from our diet forces the body to utilise fat from our fat cells to fuel some of these physiological functions – hence the term ‘burning fat’. But poorly planned and restrictive diets can go too far and deprive the body of energy to take care of day-to-day tasks. This forces the body to increase the activity of catabolic hormones and break down muscle reserves to produce energy instead. So while the weight on the scales may go down, this can be a combination of a reduction of fat tissue AND muscle tissue – not ideal. Lean body mass or muscle tissue is very energy-demanding and losing lean body mass decreases your metabolism significantly.  A dietitian can help you with a meal plan to ensure you’re only losing fat with weight loss and not valuable, metabolism driving muscle.

The outcome

When we inevitably fall off the bandwagon due to our insatiable appetite or stop the diet, our metabolism is sluggish and we can gain weight quickly, typically as fat. Cue the vicious cycle of dieting, weight loss, weight re-gain and back to dieting again which leaves most people feeling defeated.

But it’s not all doom and gloom!  Take a more holistic approach to your health which can help you achieve and maintain a healthy weight long term. Enter the Dietitian Approved Healthy Lifestyle Challenge! A challenge designed to put in place consistent, daily habits for overall health. Nothing to do with dieting. People do lose weight on our challenge, which is a by product of these healthy habits.

Here are a few tips for more holistic and sustainable weight loss:

  1. Ditch the food rules and concepts of ‘good’ and ‘bad’ foods. Incorporate a wide variety of fresh fruits, vegetables, wholegrains, lean meat, fish, dairy, legumes, nuts and seeds into your diet and allow yourself to eat foods which you enjoy in moderation mindfully.
  2. Become more aware of your hunger and satiety cues and allow these cues to guide when to begin and stop eating. If you’re full, stop eating. You don’t need to finish what’s on your plate despite what your mother may tell you.
  3. Be patient and take your time. Everyone wants to lose 5kg yesterday. Losing weight slowly is not only more maintainable, it prevents your weight loss from plateauing and allows your metabolism to adapt to its reduced energy workload. It's also far more socially enjoyable than severe restrictions.