Why diet? How eating differently affects weight loss (part two)

In part one of this article, Dr Mary Ellen Chatwin examined the basis of modern weight-loss diets, the sociocultural issues relating to dieting and how diets of different cultures affect health. In the second part, she now discusses medical disagreements on dieting and the effects of different foods on the body. In particular, she looks at the effects of low calorie and low carbohydrate diets.

Medical disagreements on slimming diets

As if social and cultural obstacles to changing diet weren’t enough, we find severe disagreements between nutrition and medical specialists as well, making the diet ‘shopper’ wonder whether science really has sorted things out. Indeed, they haven’t. Today, the two main approaches to 'slimming diets' are 'low-carbohydrate' and 'low calorie'.

Low carbohydrate versus low calorie slimming diets

The most thorough comparative study of all diets and results was carried out by the food journalist Gary Taubes in his book 'Good Calories, Bad Calories: Fats, Carbs, and the controversial science of diet and health' (2007). I strongly recommend the book; indeed it helped me decide on the course to take myself.

Low calorie diets restrict fat and sugars in most foods (examples are the low-fat yogurts, skim milk, no-sugar sauces, etc widely sold in grocers’ everywhere). Low calorie diets are less about ‘eliminating’ foods, than they are about ‘reducing calories’ in a given food. It has been said that calorie-oriented diets have 'fed' the food industry more than they have helped dieters, however. Many are based on substitutes for the foods we would normally eat, also with restrictions on the amount of food.

How different foods affect the body

Gary Taubes began research on diets through the years without having a clear opinion on which was the best theory. He dissected diets and research on diets from Banting’s to the most recent university studies over the last decades and came to some very interesting conclusions:

  • Fat in foods, saturated or not, has not been proven to make you fat or cause heart disease or any other chronic disease.
  • The greatest problem is carbohydrates in the diet and their effect on insulin secretion. The more easily-digestible and refined the carbohydrates, the greater the effect on your health, weight and well-being.
  • Sugars - sucrose and high-fructose corn syrup specifically - are particularly harmful, probably because the combination of fructose and glucose simultaneously elevates insulin levels while overloading the liver with carbohydrates.
  • Through their direct effect on insulin and blood sugar, refined carbohydrates, starches and sugars are the dietary cause of coronary heart disease and diabetes. They are most likely dietary causes of cancer, Alzheimer's disease, and the other chronic diseases of civilization.
  • Obesity is a disorder of excess fat accumulation, not overeating, and not sedentary behavior. Taubes maintains that “exercise doesn’t make you lose weight, it makes you hungry.” This is what Banting maintained two centuries ago.
  • Consuming excess calories does not cause us to grow fatter, any more than it causes a child to grow taller. Expending more energy than we consume does not lead to long-term weight loss; it leads to hunger.
  • Fattening and obesity are caused by an imbalance - a disequilibrium - in the hormonal regulation of adipose tissue and fat metabolism. Fat synthesis and storage exceed the mobilization of fat from the adipose tissue and its subsequent oxidation. We become leaner when the hormonal regulation of fat tissue reverses this balance.
  • Insulin is the primary regulator of fat storage. When insulin levels are elevated - either chronically or after a meal - we accumulate fat in our fat tissue. When insulin levels fall, we release fat from our fat tissue and use it for fuel.
  • By stimulating insulin secretion, carbohydrates make us fat and ultimately cause obesity. The fewer carbohydrates we consume, the leaner we will be.
  • By driving fat accumulation, carbohydrates also increase hunger and decrease the amount of energy we expend in metabolism and physical activity.

Reading Taubes’ book I was delighted to observe I could have foods like regular mayonnaise, butter or full-fat whipped cream (without the sugar of course), and these made no impact at all on weight loss.  Indeed I found I was less hungry - a bit of such foods was more likely to tide me over to the next meal.

Low carbohydrate diets and weight loss

Low carbohydrate diets restrict or eliminate foods with high amounts of digestible carbs such as white bread, pasta, potatoes and what are known as ‘starchy foods’ in general. These are replaced by meat, poultry, fish, eggs, cheese, nuts, seeds, soy products, etc which are higher in proteins and fats.

This approach was borne out first in 1933 in experiments during a clinical study by the Royal Infirmary in Edinburgh. Comparing the results of low and high-calorie diets, ranging from 800 to 2,700 kcal, they found average daily weight losses as follows:

high carb/low-fat diet

high carb/low protein

low carb/high protein

low carbohydrate/high fat

49g [like a modern slimming diet]




Today low carbohydrate diets are prescribed for a variety of conditions in addition to obesity, including diabetes, epilepsy, chronic fatigue syndrome and polycystic ovarian syndrome.

Calorie restricted slimming diets

Calorie restricted diets with low fats are still widely proposed as slimming diets today, as the issue of fatty foods and the ‘cholesterol’ controversy as well as other medical discussions continue.

One of the main reasons the calorie restricted diet fails in the longer term is the constant ‘hunger’ factor. High-protein diets with regular fat levels permit dieters to feel ‘full’ for much longer.

Weight Watchers

In the middle of the 20th century, an American diet was developed in New York which helped dieters stay the course, overcoming (at least in the short and medium term) the difficulties of dieting: The Weight Watchers movement and industry was born. Weight Watchers public ‘weighing in’ and testimonial confessions during meetings meant motivation to lose weight remained high from the social pressure of regular contacts with other dieters. This was seen as a strong motivator to overcome the hunger factor and stay the course.

Weight Watchers capitalised on an important element of dieting - the ‘diet buddy’ who can encourage and praise; this is still an important part of any diet. However, Weight Watchers went on to create an enormous industry of refined, low-calorie ready-to-eat foods marketed today without any need for a ‘buddy’. It isn’t clear whether these foods are truly helping people lose weight as much as they are enriching the low-cal industry. Although calorie restriction may provide quick weight loss at first, several studies have shown that the body adjusts to the new diet in more or less half a year so that it becomes harder and harder to lose weight with the same foods. The calorie restricted diets are also said to result in a loss of muscle mass in the process.

In Judith Beck’s cognitive psychology approach to dieting, she works with the dieter to examine why we ‘panic’ when we are hungry. She shows dieters how to deal with hunger as an integral part of a diet.  Meals and snacks are regularly planned so that over time ‘hunger’ becomes less of an emotionally charged issue.

Exercise and diet

George Bernard Shaw once commented, “Whenever I feel the urge to exercise, I just lie down on the sofa and rest until it goes away.” Although Gary Taubes states that “Exercise makes you hungry”, implying that it can make you eat more - something Banting discovered in the early days of his attempts to lose weight - most slimming diets prescribe the metabolic stimulation of walking, swimming, workouts or other exercises.

Regular exercise remains key to a healthier lifestyle, and genetically humans have balanced stamina and strength. When carried out hand-in-hand with a regular slimming diet, exercise raises the metabolic rate which stimulates weight loss.

 A well-known low-carb programme, the New Atkins Diet Revolution (1992) has a chapter entitled “Exercise: It’s non-negotiable”. In The Stone-age Health Programme (Eaton, Shostak and Konner, 1988) the accent is put on total human well-being, taking the best of our ancestral genetic make-up to create a healthy lifestyle. The authors recommend regular cardiorespiratory endurance exercises while increasing muscular strength and flexibility. However, the authors warn against intensive exercise in situations where dieters are severely restricting calories, as this can lead to severe loss of muscle and bone mass.

A final word

Making the decision to diet should be carefully studied. A diet is a choice to make a life-style difference. Hopefully, this two-part article points to some of the issues to be considered. As I find the pounds slipping away, I always keep in mind the words of a very good friend who said, “No food tastes as good as it feels to be slim.”  Now I believe her.

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Why diet? How eating differently affects weight loss (part two)
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