Why Following a Restrictive Calorie Diet Long Term May be Sabotaging Weight Loss

The weight loss messages out there is that calories need to be restricted in order to lose weight. I have seen many people, especially women, restricting to a 1200 calorie diet, or lower, in order to sustain their weight loss (this is the nutrition requirements for to a toddler!). A lot of women face calorie restrictive diets due to their previous success with weight loss on a specific calorie intake per day, however their weight is plateauing on the exact same diet. If an individual is exercising and is theoretically burning more calories than they are consuming then why are they at a plateau or even begin to re-gaining weight?

Bodies physiological response to weight loss

When we follow a low calorie diet for an extended period of time the body actually adapts to that calorie load, therefore the body will begin to burn less calories at rest, this is called metabolic adaptation, better known as metabolic damage or starvation mode. Metabolic adaptation is the bodies response to long term caloric restriction or starvation. Specifically, it has been estimated that for each kilogram of lost weight, calorie our metabolism burns 20–30 kcal/day less and additionally appetite increases by about 100 kcal/day, above baseline level prior to weight loss. Metabolic adaptation can be attributed to set point theory that suggests our bodies have a comfortable weight; when we lose weight, our body has mechanisms to bring us back to our set point. These mechanisms include:

o Leptin decreases: Leptin is our satiety hormone that is stored in fats cells; leptin signals fullness after a meal. As we lose weight, fat cells shrink, and leptin levels drop, therefore fullness after meals decreases.

o Ghrelin increases: Ghrelin is the hunger hormone, that increases our appetite. Studies demonstrate that after weight loss, ghrelin increases, therefore our appetite increases!

o Cortisol increases: Cortisol is a stress hormone. Cortisol is released with restrictive diets and/or extreme exercise. Increases in cortisol actually slow metabolism, decreasing the ability for sustained weight loss.

Reverse Dieting

The impact of chronic restrictive calorie diets points to the fact that restricting calories long term is unsustainable, therefore it is recommended for those who have restricted calories for a long period of time to build up calories overtime, this is often termed reverse dieting. Reverse dieting holds the idea that increasing calories slowly overtime will boost up the number of calories you burn at rest, also termed basal metabolic rate (BMR), therefore your body will be burning more calories allowing you to consume more food, restoring metabolism back to a pre-diet rate. There is not much peer-reviewed literature on reverse dieting, this approach heavily relies on anecdotal success stories. However many sports dietitians’ utilize reverse dieting as a way to restore metabolism after periods of calorie restriction, as seen with competing bodybuilders. Reverse dieting stresses the importance of slowly increasing calories by 50- 100 kcal per week, in a step-wise manner.

People that may require a reverse diet include:

• Thos who have plateaued with their weight loss, despite following a calorie restricted diet.
• Those maintaining weight loss at miserably low calories, ultimately impacting overall quality of life.

Takeaways

I wanted to raise some awareness today on some take-home messages:

1. Restricting calories in the long term may be an unsustainable approach that ultimately slows down metabolism, therefore reverse dieting may need to be considered.

2. If you are concerned you may be eating too few calories for your body, it is important to speak to a registered dietitian to assess your current caloric intake as well as strategies to work towards increasing your daily calories to boost energy and overall quality of life.

3. It is important to be aware that companies and non-nutrition professionals providing extremely low calorie diets are not considering the long term implications of the bodies mechanisms to regain weight, ultimately making consumers of these diets believe they have “no self control”.