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What is Starvation Protection Mechanism?

Posted by Aisling Murray on

To lose weight you must create a negative energy balance: calories taken in are less than calories expended. Result: Fat, glycogen and muscle are used for energy to make up the caloric deficit and ideally weight is lost and fat stores are reduced. However, losing weight and losing fat are two different stories. Weight loss does not necessarily equal fat loss.

Outcome 1 of starvation diet

In order to achieve any long lasting weight-loss you need to “fool” the starvation protective mechanism of the body.  Very low calorie diets may work for a certain length of time (2-3 weeks) however two things can happen when an individual follows a low calorie diet for too long. The first is you find you are too hungry, making it impossible to continue. You may get headaches from lack of food and sustenance or feel lightheaded or even feel faint. You then cease to follow this low calorie diet any longer thus putting on the weight you may have lost because you have hindered your metabolism.


Outcome 2 of starvation diet

The second outcome from following a low calorie diet is your body believes it is starving/in a famine environment. Your body does not know you are living in an environment surrounded by food; all it knows is food is scarce, the reasoning behind the scarcity is not important.  As a result, your body goes into what’s known as starvation protective mechanism. Very low calorie diet is described as <1200 calories for women and <1800 for men.  Starvation protective mechanism involves the body making the most of the calories it does get from food and drink. 

The science behind the negative effects of crash diets

Your body responds to very low calorie diets in a very negative way and your metabolism become affected as a result. The initial reaction by the body if too few calories are consumed (crash diets) is to protect its fat stores. As a result, it uses lean tissue or muscle to provide the body with calories in order to function and perform biological processes.  For someone who eats their RDA of calories then the body will function ideally as it’s getting calories from food and will break down fat if more energy is required. This is how people who eat little and regularly maintain a healthy weight. However, when your body feels threatened (crash diet), the body’s leptin levels (a hormone that breaks down stored body fat) decreases and only allows fat cells to release energy in order to sustain your most basic bodily functions. Even though you continue to follow a crash diet/low calorie diet and think you are doing well by losing weight, you are in fact losing muscle and not fat (may lose a small portion of fat). Your body has shut down its fat-burning ability in order to conserve energy.

To make situations worse, when you do consume food your body stores the nutrients including fat (calorie reservoir) for use later. Instead of burning the fat straight away for day to day activities, your body “panics” into thinking that calories will be in short supply again so it stores them in the form of fat. As a result, fat cells increase and you end up gaining weight. This is how yoyo dieting comes into play as you may damage your metabolic rate from constant dieting.


Sugar Information Event

Whelehans pharmacy are teaming up with a number of health professionals to hold a Sugar Information Event on Thursday March 3rd at 7pm in the Greville Arms Hotel. We will have interesting speakers and inactive demonstrations to illustrate both the dangers of sugar and show how much sugars we are actually eating. There will be lots of tips to help you reduce your sugar intake without reducing your enjoyment of food. It will be of great interest to parents and kids to help learn fun facts and ways to reduce sugar. Parents are especially welcome to bring kids along. You will have the chance for free advice from diet and health experts on the night. It is a free to attend; call Whelehans at 04493 34591 to book your free place.


Aisling Murray has a Bachelor of Science in Nutrition and offers a one to one specialist nutrition service at Whelehans Pharmacy. Call Whelehans at 04493 34591 for an appointment. Aisling’s Nutriton Clinic costs only €10 per week.



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