Why a Low Calorie Diet Doesn't Work

For many years the old mantra of calories in and energy out has been used in the media and some areas of the fitness industry to explain that if you consume the average amount of calories (males 2500/females 2000) needed for the body to perform its daily functions than you will not put on any weight. If you use up more energy than you consume, you will therefore lose weight and if you consume too many calories the body needs than it will store any excess as fat. This is a commonly held belief across the general public and the scientific world and has been upheld for many years. However if you look more closely at the data and the studies that have been done in recent years you will see that it's not as simple as calories in and energy out. France consumes a higher than average amount of calories as well as the highest consumers of fat at 42% of daily intake but have the second lowest obesity rate in all of Europe! Whereas some countries such as Serbia and Montenegro have low calorie intakes but much higher obesity levels. So what is going on? Research is now suggesting that it may be a combination of a variety of influences such as genetics, hormones and the environment. It was observed that some animals and humans appear to have an increased susceptibility to gaining weight compared to others. Studies showed that weight gain in obesity prone mice is higher than wild mice fed the same high fat diet. Obesity prone mice seem to prefer high fat diets. Subjects with a predisposed tendency to become obese seem to have an impaired ability to increase the speed of burning fat and carbohydrates in response to a high fat diet. Women with a family history of obesity had a stronger risk of gaining weight when exposed to a high fat diet than those who had none. There are many hormones in the body that can influence what we eat, how much we eat and how often. Ghrelin is released to stimulate hunger when the body needs more energy. The interesting thing about this is it has an inverse relationship with BMI. So in thin people it drives them to consume more and in overweight and obese people who have lost weight, the levels increase as well to encourage the body to return to its original weight. This is why weight loss can be hard to maintain in the obese population. In obese humans the central nervous system just like lean muscle (see last blog for details) can become insulin resistant and signals do not reach the brain to tell it the stomach is full and therefore too much is consumed resulting in an increase in body weight. A study in 2002 (Pirozzo) proved that although a calorie and fat restricted diet worked for the first 6 months over a longer period of time, 12 and 18 months, weight began to slowly creep back on. Other studies have shown the average maintained weight loss, 3-5 years after starting a low calorie diet was only 3KG. The average regain in weight at the 3-5 year follow up represented 76-85% of the initial weight lost (Grodstein et al, 1996 and Anderson et al, 2001). So as you can see it's a combination of factors that can cause obesity rather than simply the amount of calories you are consuming. It seems that one factor will not cause weight gain but a series of events will, such as a person who has a tendency for weight gain consuming processed foods that are high in fat and carbohydrates on a regular basis and is not active. If you're overweight or obese it's better to try to consume natural foods which are high in proteins and fats, such as meat, fish, chicken and dairy products that will keep you fuller for longer and exercise regularly rather than relay on a low calorie and fat diet.