Why fad diets are bad for you.

There are so many different diets out there, mostly with no scientific basis and an apparent quick fix for weight loss.


Some will work initially but many of them are not maintainable for long-term life and inevitably the weight just piles back on.


There are many meal replacements diets, some providing as little as 440kcal per day.  It is a real concern that any one should be consuming as few as 440kcal a day, which is definitely not compatible with a healthy lifestyle.   There are diets based on your blood group, alkaline diets, and the cabbage soup diet, even the werewolf diet.


Fad diets often leave you dehydrated, feeling tired, with malnutrition and giving you digestive problems.


A healthy weight loss diet should be based on a balanced diet, with the right amount of vitamins, minerals and fibre, the correct proportions of macronutrients (carbohydrates, protein and fat) and in the correct quantities. Your calorie intake should fit with your level of activity and your nutrition is a major portion of a healthy lifestyle. 


When adjusting your diet to try and lose weight, you should feel you could maintain this way of eating for good and not just for the short term. If not you will inevitably fall back into your previous ways and put the weight back on.  Many people are not doing this, but picking a fad diet and ending up with their weight fluctuating and sometimes very dramatically, feeling more and more disheartened with each new diet they try.


Weight loss should be a very gradual process and it takes patience, but the weight loss will be sustainable and healthy.


To help explain why fad diets based on calorie restriction do not work I have made up a case study to demonstrate.


Meet Sara, she’s 30 years old and 5ft 5 inches and weighs 80kg. Sara wishes to lose weight, she’s looked online and found a calorie restricting diet which advises to consume 1000kcal a day, and claims the weight will drop off in weeks.


So Sara’s actual calorie requirement per day is 2,114kcal i.e. she needs to consume 2,114kcal per day to maintain her current weight.


The new diet will provide Sara with just fewer than 50% of her calorie needs, so well below her basal metabolic rate, which is the amount of energy required at rest.   Therefore when Sara starts the new diet her body will be in starvation mode.


In starvation mode the body is doing all it can to ensure survival.  The brain can only survive on carbohydrate for energy and this comes from glycogen stored in the liver.  On the first day of the diet all the bodies glycogen stores, and any carbohydrates consumed plus muscle glycogen stores, will be totally used up.


Glycogen is stored in the body hydrated (this means with water) so with glycogen loss also comes water loss.  Three grams of water is stored with every one gram of glycogen.


So if Sara initially had 300grams of glycogen stores, she would lose 1.2kg of weight in the first day.  Plus Sara’s metabolic rate will be slowly down by up to 20% in the first 24 hours, as her body is not getting the calories needed.


The body can actually make its own glucose once the glycogen stores have been used up.  It normally starts doing this by using amino acids (these are the building blocks of protein), and if dietary intake of protein is low the body can use its own stores of protein i.e. skeletal muscle.


As with glycogen, muscle is stored with water and there are four grams of water for every one gram of protein.  If Sara’s body breaks down 100grams of protein this will amount to a weight loss of 500grams.  So Sara’s weight loss after only two days will be 1.7kg.


Sara is probably also feeling tired and dehydrated, and what she may not be aware of is that she has lost no body fat but only water, body stores of glycogen and lean tissue.


It is also likely that Sara will not be consuming adequate vitamins, minerals and essential fatty acids, and this will be eventually evident in the appearance of her hair, skin and nails.


So what happens if Sara continues the diet?  Protein breakdown will be very extensive in the first few weeks, and although fat stores will be abundant the body will not be able to effectively mobilise these stores.  This is because the bodies fat burning ability decreases when carbohydrates are not plentifully available, and during starvation mode the body will inhibit the release and burning of fat plus try to increase fat storage.


Eventually the body would go into ketosis, where by it creates energy by breaking down fat,  and ketone bodies are produced when store fats are broken down.


Ketone bodies can mask your hunger even though the brain is demanding carbohydrate. Excessive levels of ketones (ketoacidosis) in the blood can make you feel tired, give you headaches, and cause excessive thirst and urination. Symptoms can become severe in the late stages of ketoacidosis.


Weight loss would continue but weight loss per week would decrease.  Several weeks into the diet no further weight loss will occur as the body has learnt to adapt to the new diet and bodily functions will be dramatically less efficient.   At this point Sara could drop her calorie intake even further to kick-start her weight loss again or the most likely response is to start eating normally again.  The body will see this as binging and these extra calories will be stored very easily as fat and Sara’s weight increase.


So the take home message is more often fad diets don’t work for long-term weight loss, and they are generally not very healthy.   Weight loss should progress slowly but surely and healthy eating is a major part of a healthy way of living.  Plus of course exercise should also be combined into every ones lifestyle.


Please do not hesitate to contact me for any questions, as always I will be happy to help!