The Problem with Low-Calorie Diets For Weight Loss
We’ve been told for so long that weight loss is easy if we could just eat less and move more. Calorie-counting has become the popularly accepted way to lose weight and keep weight off. But if it’s really that easy, how come many countries are facing an epidemic of obesity and related conditions such as type 2 diabetes? And, on an individual level, why do so many people struggle to lose weight even when they eat within calorie limits or, more commonly, lose weight and then put it all back on again?
It is of course true that creating a calorie deficit – eating fewer calories than you burn – can lead to weight loss. When the body lacks calories, it has a better chance of burning excess body fat. However, the human body is not a laboratory machine –the balance of calories going in versus calories being burned is affected by many factors, not least of which is the individual’s metabolic rate and their insulin response to food.
For many people, low-calorie diets bring more problems than they solve, for example:
- When the body gets the message that food is no longer plentiful, it may slow down the metabolism to preserve energy, making it more difficult to lose or maintain weight with the same amount of food. This is why some people reach an impasse with dieting: they are eating very little but are unable to lose the excess weight.
- Calorie restriction usually requires good willpower. Unfortunately, willpower tends to run out eventually. The feeling of having been restricted or deprived in food choices can lead to over-eating or eating readily-available processed or sugary treats, often because cravings become stronger as the body looks to take in more food in response to the perceived scarcity.
- Low caloric intake can reduce the body’s supply of the dietary nutrients it needs to support good functioning of the glands and organs involved in energy and weight management, such as the thyroid. This then negatively affects weight-loss efforts and may drive us to eat more in order to obtain the vitamins, minerals, proteins and fatty acids the brain and body need for overall health.
- Caloric restriction encourages us to ignore hunger. This can be stressful for the body, potentially disturbing the stress response system and resulting in greater fat storage, as well as dysfunction in the hormonal regulation of hunger, daily sleep-wake and energy patterns.
All Calories Are Not Created Equal
In addition to these problems with low-calorie diets, when we judge foods only by their calorie count, we are missing a whole lot of other information about them.
A more healthy and effective way to lose weight and keep it off is to assess food on 2 important criteria:
- Nutrient profile, including nutrient density
- The hormonal response the food is likely to trigger in the body
Foods are not all created equal and neither are calories. 100 calories from cake have neither the same nutrient profile/density nor the same hormonal effect as 100 calories from avocado. The nutrients and how the body responds to the food overall have a significant role to play in weight management because these factors affect how much we eat and how incoming food energy is used and stored in the body.
Low-calorie diets tend to be low-fat diets because fat contains more calories per gram than protein and carbohydrates do. The body needs fatty acids, however, to maintain the brain and nervous system, create hormones and help with the absorption of the fat-soluble vitamins A, D, E and K. Low fat intake can lead to depletion of these important vitamins and contribute to mood, immunity and other disorders. Natural fats found in foods help to fill us up and give us feelings of satisfaction. Importantly, they also have minimal effects on blood glucose levels, helping to keep our levels stable and staving off cravings.
Avoiding foods higher in fat or calories can also have the incidental effect of reducing intake of reliable protein sources such as nuts, meat, fish and eggs. Like fat, protein contributes to filling us up at meals and keeping blood glucose stable. Protein also has an essential role in providing the body with the raw materials for creation, maintenance and repair of important tissues such as muscle, hormones, neurotransmitters and skin.
Low-fat foods chosen for their low calorie count often include grain-based and processed foods that are high in starch, sugar and additives and low in nutrients. The higher the sugar content of a food, the more it has the potential to cause sharp spikes and falls in our blood glucose levels. Frequent highs and lows in blood glucose can drive food cravings but, more importantly, they have been seen in studies to predispose people to metabolic disorders such as excessive weight gain, diabetes and high blood pressure.
Glucose and Insulin in Weight Management
Whenever blood glucose rises, the hormone insulin rises to take glucose and other nutrients out of the blood stream and into the cells where they are needed. This mechanism keeps blood glucose within safe parameters. If insulin levels remain chronically high due to a high-sugar diet or because the glucose-insulin mechanism starts to malfunction, a cascade of health problems can occur, partly because both glucose and insulin are inflammatory when out of control. High glucose and insulin in the blood can be a significant obstacle to weight loss because:
- Glucose that is not taken up by cells for use can end up stored as fat in adipose tissue.
- Insulin is, broadly speaking, a ‘fuel storage’ hormone. It works antagonistically with the ‘fuel-burning’ hormone glucagon. When one is high, the other is low. So, plenty of insulin in the bloodstream prevents the body from burning body fat for fuel. This makes it hard to burn excess body fat and lose weight.
Carbs Are Not Your Friend
While commonly recognised sugary foods like sweets, cakes and biscuits can challenge blood glucose and insulin mechanisms and trigger the problems discussed above, most people recognise these foods as potential obstacles to weight loss. What is less well-known is that starchy foods such as grains and root vegetables can also be problematic for blood glucose and insulin control when eaten to excess. Starches are in fact chains of glucose molecules that are uncoupled once we eat them so that the glucose molecules can pass into the bloodstream.
The fibre content of unrefined foods high in carbohydrates such as wholegrains and root vegetables helps glucose from these foods to go into the bloodstream slower than from refined carbohydrates such as white-flour products (pastries, white bread, white rice, etc.). Eating high-carbohydrate foods with protein-rich foods or a little naturally-occurring fat can also slow down the rate at which glucose enters the blood stream.
However, while a slower release of sugar into the blood helps avoid sharp blood glucose rises, all high-carbohydrate foods will result in a higher quantity of glucose going into the bloodstream compared with protein and fat-rich foods. This is why the British Association for Nutrition and Lifestyle Medicine (BANT) suggests that grains and starchy vegetables are best restricted to no more than a quarter of the plate and that, when excess body fat is an issue, this quarter portion is reduced even further.
A growing number of doctors and nutritionists working in the field of weight loss and type 2 diabetes help patients to identify high-carbohydrate foods and adjust their intake according to their individual needs. To compensate for the lower carbohydrate intake, protein-rich foods such as meat, fish, eggs, nuts, beans and tofu are placed at the heart of the diet, with abundant leafy green and colourful vegetables eaten without restriction. These are the parts of vegetables that grow above ground, rather than the tubers in which the plant stores its starch.
Unprocessed oils such as extra virgin olive oil complement the fats that occur naturally in protein-rich foods, while herbs, spices, seeds and low-sugar fruits such as berries and apples add an extra nutritional boost. Patients adopting this way of eating – who must be medically monitored if they are taking prescription medications – report less hunger, fewer food cravings and more balanced energy levels.
Calories Count But Hormones Rule
Part of the success of a weight-loss strategy that focuses on the nutrient quality and hormonal effects of food is the way such an approach tames cravings and reduces hunger, resulting in fewer calories being consumed. Much of the success, however, appears to be due to resolving chronically elevated insulin levels and uncontrolled blood sugars, and therefore allowing body fat to burned. This might be even more important for people with a tendency towards blood glucose and insulin dysregulation, whether because of genetics or newly-discovered factors such as imbalances in the microbes that live in the gut. The one benefit that cannot be stressed enough, however, is the fact that a weight-loss strategy that doesn’t involve going hungry is one that is more likely to be sustained in the long term.
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