Nutrition gurus regularly appear on the scene, promising that a certain kind of diet, such as Atkins, raw food, low-carb, or veganism, will affect the metabolism in such a way that you can eat as much as you want (within the constraints of their nutritional regime) and still lose weight with a daily intake of 5000 kcal.
With a grain of truth, to be exact. Certain regimes do actually lead to your wanting to eat less, which means that the claim that ‘you can eat as much as you want’ and still lose weight is sort of true. But it isn’t magic, and it doesn’t work for everyone, as some people don’t let themselves be fooled and still consume more calories than they need, only now it’s not in the form of cake, but chicken or broccoli.
Research shows that a high-protein diet curbs your appetite and that people consume an average of 440 kcal less when their food is high in protein (Weigle et al. 2005).
One reason for this is that protein leaves us feeling full for longer and has less of an impact on blood sugar levels. While simple carbohydrates like sugar and white flour enter the blood stream rapidly, provide a lot of energy very quickly, and are followed by a ‘crash’, dietary fibre (e.g., from fruit, vegeta- bles, or wholemeal products) cause sugars to be absorbed into the blood- stream at a slower and more constant rate, so they make us feel full for longer, thereby avoiding snack attacks and sugar rushes.
Protein and fat are also ab- sorbed more slowly and provide the body with energy for longer. So while a piece of cake with 500 kcal and a piece of turkey meat with broc- coli also containing 500 kcal will provide the same amount of energy, the cake is processed more quickly and delivers its energy straight away. This can result in pleasurable feelings, just like the consumption of coffee and nicotine, and even cocaine — all of which have a stimulatory effect.
After the rush comes the crash, as we feel the sugar levels in the blood fall again. This is an unpleasant sensation, stoking the desire to do something to counter it — preferably with something that will rapidly raise our blood sugar levels again.
The paradox here is that a diet containing lots of sugar and white flour products often leaves us feeling less contented, even though eating those delicacies is considered ‘a treat’. They leave us with the feeling that we can never quite eat enough as we constantly strive to regulate our blood sugar at a higher level. MedicineNet (2015) additionally explains that people whose blood sugar level is high for a prolonged period of time can eventually become so accustomed to it that they feel symptoms of hypoglycaemia when their sugar level sinks to nor- mal.
Their heart rate increases, they begin to tremble and feel restless, anxious, and dizzy. These are similar to withdrawal symptoms. High-fibre foods such as fruit also contain a lot of sugar, and similarly, wholemeal bread often contains the same number of carbohydrates as white bread, but the fact that the energy is taken up more slowly means they don’t cause sugar rushes or crashes.
The energy is released in a more constant way. High-fibre foods also have much more volume. A pound of carrots contains fewer than 200 kcal, and it’s far easier to polish off one 50-gram Snickers bar (242 kcal) as a snack than half a kilo of carrots. If we assume that vegetables contain an average of 30 kcal and fruit has about 60 kcal per 100 g, then we see that it is physically almost impossible to overeat on raw foods.
A large, muscular man with a daily energy requirement of 2500 kcal would have to eat 5 kg of fruit and veg per day to gain weight. Even for people with naturally large appetites, that would be quite a challenge.
The secret of super-diets is that they lead people to cut their calorie intake without feeling that they are denying themselves anything, because their calo- ries now come from high-protein or high-fibre sources, which reduces their ap- petite.
But that doesn’t mean that the principle of caloric balance no longer ap- plies. It is, of course, just as possible to lose weight by eating 1000 kcal of cake per day as by eating 1000 kcal of vegetables or protein. This is proven by the case of two men, a teacher and a university professor, who both lost a lot of weight by eating ‘unhealthy food’ but always only up to a certain calorie limit.
The teacher, John Cisna, ate 2000 kcal of McDonald’s every day and went from 127 kg down to 101 kg in six months and lowered his BMI from a previously severely obese level to 31 (Pawlowski, 2014). Mark Haub, a professor at Kansas State University, consumed 1800 kcal a day in the form of sweet snacks like doughnuts and Twinkies, and lost 12 kg in
two months, taking him from being slightly overweight to within the normal weight range.
Surprisingly, his blood test results improved, despite his un- healthy diet: his levels of ‘bad’ LDL cholesterol fell by 20 per cent and his ‘good’ HDL cholesterol rose by the same amount, while his blood lipid levels sank by 39 per cent (Park, 2010). Larger-scale studies comparing different eating regimes showed similar re- sults.
Golay et al. (2000), for example, gave obese hospital patients a diet of 1100 kcal per day, either in the form of a low-fat diet or as a diet low in carbohy- drates but high in fat. The two groups lost the same amount of weight, and both saw similar and significant improvements in their blood test results and their blood pressure, irrespective of the diet they had been fed.
The same group of researchers had carried out a similar experiment four years earlier (Golay et al., 1996), and in that case, too, patients who were given a diet of 1200 kcal a day either in the form of a high-carbohydrate or a low-carbohydrate diet lost the same amount of weight.
They also saw great improvements in their blood test results. The group on the low-carb diet showed a significant drop in their blood sugar levels, however, unlike the high-carb group. The amount of sugar in a diet is also irrelevant, as long as the overall number of calories consumed remains the same. Surwit et al. (1997) placed 42 women on a high-sugar or a low-sugar diet to lose weight. Both groups lost the same amount, both saw improvements in their blood test results and their blood pressure, their appetites shrank over time, and both groups’ general mood im- proved.