As anyone who has been on a diet knows, it can be an uphill battle after cutting down on consumption. No sooner has one lost a few kilos than they come back again, with a few more added on.
Now a group of eminent American scientists has produced a study to support what many dieters have long suspected: what you eat matters more than the calories consumed. So, you will have more dieting success eating a bowl of lettuce of about 1000kJ than a slice of bread, worth about the same number of kilojoules. The answer lies in the complex processes of our metabolism, say the researchers.
The study, “The carbohydrate-insulin model: a physiological perspective on the obesity pandemic” published in September in the American Journal of Clinical Nutrition, posits a replacement for the century-old model of “calories in equals calories out”, or the energy balance model (EBM).
The EBM says weight loss occurs when more energy is expended than energy consumed. This may sound logical, but in the end doesn’t tally, according to the carbohydrate-insulin model (CIM) study. “Conceptualising obesity as a disorder of energy balance restates a principle of physics without considering the biological mechanisms that promote weight gain,” says the study.
This conventional thinking has not helped to stem the obesity pandemic. Instead, it is increasing. The situation is serious in SA, where, according to the 2017 South African National Income Dynamic Survey, the majority of adult women were overweight or obese (24% overweight and 35% obese) while 16% of adult men were overweight and 8% obese.
Prof Salome Kruger of the Centre of Excellence for Nutrition at North West University says the gender disparity may be because a large proportion of men in SA are in the low-income group, where their jobs and methods of commuting necessitate high physical activity. “Women from the same income group may be unemployed or working in jobs where they are sedentary ... they may also spend more time in environments where they have access to food, such as their homes, in households and shops.”
In contrast to the EBM, the CIM says that overeating is in fact not the main cause of obesity. It states that the worldwide obesity epidemic is more a result of the modern-day diet, which is characterised by foods with a high glycaemic load (GL), and especially refined and processed carbohydrates that are digested and absorbed into the system fast.
The researchers found that high-GL foods — such as fast-food takeaways and commercially produced biscuits and sweets — cause hormonal responses in the body that fundamentally change the metabolism. These outcomes include increased fat storage, with resulting weight gain and obesity.
For most individuals, eating highly processed carbohydrates will increase the secretion of insulin in the body, at the same time suppressing the production of glucagon.
Fat cells in turn then store more energy. The body is left with less energy for its other activities, such as muscle function.
When the brain perceives this energy depletion, it registers it as hunger. So while we are still feeling hungry we are gaining excess fat.
“Anyone who tries to lose weight by eating only small amounts of refined starches will get extremely hungry, and due to low availability of metabolic fuel, their metabolic rate will also drop and they will burn less energy for body functions,” says Kruger.
“I agree with the authors of this paper that it is important that scientists should work together and not just try to prove each other wrong. There is some truth in the assumptions from both models. None of these two is the final model, and all the evidence from sound research should be used to help people living with obesity to improve their quality of life.”
However, the belief in the model that “calories in equals calories out” has been a “huge frustration for me as a dietitian”, says Philippa Bramwell-Jones of Johannesburg-based practice Intuitive Nutrition. “It’s fundamental to look at biochemistry first. Insulin is the dominant anabolic [storage] hormone in the body. It promotes glucose uptake while suppressing the release of energy from our fat stores and promoting fat and glycogen [stored carbohydrate] stores.
“Insulin resistance plays a part in losing ‘sticky’ weight — the type that is hard to budge. Insulin resistance increases hunger and fatigue and can lead to irritability. The idea that 500 calories of vegetables has the same biochemical effect as 500 calories of bread makes absolutely no sense. Just like the old food pyramid, this model was presented to the public in a way that it somehow became the consensus regarding weight loss.
“It is not the quantity of the food we eat we should be focused on, but rather the quality. The carbohydrate-insulin model focuses on physiological mechanisms and how the information we get from food drives hormones, metabolic pathways, gene expression and the gut microbiome in ways that influence fat storage.”
The CIM recommends reducing refined grains and added sugars; emphasising low-GL carbohydrates; consuming less-processed grain products; increasing intake of nuts, seeds, avocado, olive oil and other healthful high-fat foods; maintaining an adequate intake of protein, including from plant sources; and avoiding potentially “obesogenic” food additives (artificial chemicals that may affect hormone balance and the way we make and store fat).
Bramwell-Jones adds: “If you are someone who is finding it difficult to lose weight, it is worthwhile to look at your insulin levels. If you do have elevated insulin levels, a dietary and lifestyle intervention can help normalise them. It’s not about calorie-counting or restricting your food intake, and it’s not about excessive exercise. In my experience, the solution is to slowly correct biochemical imbalances through improving the quality of the food you are eating. This includes using healthy fats as your source of energy (avocados, olive oil, oily fish).
“Also, focusing on healthy protein to support and promote satiety (lean meat, chicken, fish). Instead of processed, refined carbs like white flour, choose starchy vegetables that are full of good fibre and nutrients. These include pumpkin, beetroot and baby potatoes, as well as whole grains such as rice and quinoa, and seeded bread.”
Society has, historically, criticised overweight individuals by creating a one-dimensional view that overweight equals overeating
— Philippa Bramwell-Jones
The main author of the CIM study, Dr David Ludwig, an endocrinologist at Boston Children’s Hospital and professor at Harvard Medical School, says there are biological causes to weight gain that the EBM does not take into account. “During a growth spurt, for instance, adolescents may increase food intake by 1,000 calories a day. But does their overeating cause the growth spurt or does the growth spurt cause the adolescent to get hungry and overeat?”
By the same token, when one is older it seems it becomes easier to put on weight and harder to shift it. Dr Dhesan Moodley, a Johannesburg-based specialist in functional and anti-ageing medicine, says this is often due to hormonal imbalances that come about during menopause and andropause. “Both a hormonal imbalance or hypothyroidism could increase appetite. To compound the issue, patients with these conditions gain weight even if they do not increase their calorie intake because their metabolism slows and their fat storage increases.”
The CIM study shows “the body’s healthy response to food is altered when the diet is mainly high-GI foods such as sugar, bread and similar carbs”, he says.
Moodley adds that the EBM is limited as a model in that it does not take possible hormonal imbalances into account, or the effects of emotional and stress eating, organic causes such as hypothyroidism, sedentary lifestyle, convenience eating or the addictive taste of high-glycaemic index foods.
“An effective management plan begins with thorough investigation and testing of sex hormones, thyroid hormones, salivary cortisol levels to assess stress levels as well as nutrient deficiencies,” he says. “Depending on these results, the underlying issue is addressed. For example, if thyroid hormone is low, it can be supplemented with thyroid hormone treatment.”
Bramwell-Jones calls for a more compassionate approach: “Society has, historically, criticised overweight individuals by creating a one-dimensional view that overweight equals overeating. It’s time for this type of thinking to change. Grief, trauma, chronic pain, depression, stress, addiction, thyroid and other hormone imbalances have huge physiological effects which can drive fat storage and reduce weight loss potential. I have clients with crippling low self-esteem after years of following both fad diets and calorie restriction. I feel saddened when clients report that they’ve been told to ‘eat less and exercise more’. It’s not the approach that, in my experience, works.
“Find a health professional who will listen to you, who will take the time to test and explain your biochemistry, who will support you through the process of change, looking at you as an individual with your own unique life experiences and current circumstances.”
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