What is Low Carb Diet?
Low-carbohydrate diets or low-carb diets are dietary programs that restrict carbohydrate consumption, often for the treatment of obesity or diabetes.
Foods high in easily digestible carbohydrates (e.g., sugar, bread, pasta) are limited or replaced with foods containing a higher percentage of fats and moderate protein (e.g., meat, poultry, fish, shellfish, eggs, cheese, nuts, and seeds) and other foods low in carbohydrates (e.g., most salad vegetables), although other vegetables and fruits (especially berries) are often allowed.
Low Carb Diet are sometimes ‘ketogenic’ (i.e., they restrict carbohydrate intake sufficiently to cause ketosis).
The term “low-carbohydrate diet” is generally applied to diets that restrict carbohydrates to less than 20% of caloric intake, but can also refer to diets that simply restrict or limit carbohydrates to less than recommended proportions (generally less than 45% of total energy coming from carbohydrates)
In Western diets, most meals are sufficiently high in nutritive carbohydrates to stimulate insulin secretion. The primary control for this insulin secretion is glucose in the bloodstream, typically from digested carbohydrate. Insulin also controls ketosis; in the nonketotic state, the human body stores dietary fat in fat cells (i.e., adipose tissue) and preferentially uses glucose as cellular fuel. Diets low in nutritive carbohydrates introduce less glucose into the bloodstream and thus stimulate less insulin secretion, which leads to longer and more frequent episodes of ketosis. Some research suggests this causes body fat to be eliminated from the body, although this theory remains controversial, insofar as it refers to excretion of lipids (i.e., fat and oil) and not to fat metabolism during ketosis.
Health Benefits of Low Carb Diet
Low-carbohydrate diets are used to treat or prevent chronic diseases and conditions, including cardiovascular disease, high blood pressure, metabolic syndrome, diabetes.
Low Carb Foods List – Low Calorie Foods
- Vegetables: Spinach, broccoli, cauliflower, carrots and many others.
- Fruits: Apples, oranges, pears, blueberries, strawberries.
- Nuts and Seeds: Almonds, walnuts, sunflower seeds, etc.
- High-Fat Dairy: Cheese, butter, heavy cream, yogurt.
- Fish: Salmon, trout, haddock and many others. Wild-caught fish is best.
- Eggs: Omega-3 enriched or pastured eggs are best.
- Fats and Oils: Coconut oil, butter, lard, olive oil and cod fish liver oil.
- Meat: Beef, lamb, pork, chicken and others. Grass-fed is best.
Low-carbohydrate diet advocates in general recommend reducing nutritive carbohydrates (commonly referred to as “net carbs”, i.e., grams of total carbohydrates reduced by the non-nutritive carbohydrates) to very low levels. This means sharply reducing consumption of desserts, breads, pastas, potatoes, rice, and other sweet or starchy foods. Some recommend levels less than 20 g of “net carbs” per day, at least in the early stages of dieting (for comparison, a single slice of white bread typically contains 15 g of carbohydrate, almost entirely starch).
Raw fruits and vegetables are packed with an array of other protective chemicals, such as vitamins, flavonoids, and sugar alcohols. Some of those molecules help safeguard against the over-absorption of sugars in the human digestive system. Industrial food processing depletes some of those beneficial molecules to various degrees, including almost total removal in many cases.
Low Carb Diet Science:
Also, a category of diets is known as low-glycemic-index diets (low-GI diets) or low-glycemic-load diets (low-GL diets), in particular the Low GI Diet. In reality, low-carbohydrate diets can also be low-GL diets (and vice versa) depending on the carbohydrates in a particular diet. In practice, though, “low-GI”/”low-GL” diets differ from “low-carb” diets in the following ways. First, low-carbohydrate diets treat all nutritive carbohydrates as having the same effect on metabolism, and generally assume their effect is predictable. Low-GI/low-GL diets are based on the measured change in blood glucose levels in various carbohydrates – these vary markedly in laboratory studies. The differences are due to poorly understood digestive differences between foods. However, as foods influence digestion in complex ways (e.g., both protein and fat delay absorption of glucose from carbohydrates eaten at the same time) it is difficult to even approximate the glycemic effect (e.g., over time or even in total in some cases) of a particular meal.
Another related diet type, the low-insulin-index diet, is similar, except it is based on measurements of direct insulemic responses (i.e., the amount of insulin in the bloodstream) to food rather than glycemic response (the amount of glucose in the bloodstream). Although such diet recommendations mostly involve lowering nutritive carbohydrates, some low-carbohydrate foods are discouraged, as well (e.g., beef).Insulin secretion is stimulated (though less strongly) by other dietary intake. Like glycemic-index diets, predicting the insulin secretion from any particular meal is difficult, due to assorted digestive interactions and so differing effects on insulin release.
A perception developed that getting energy chiefly from dietary protein rather than carbohydrates causes liver damage and that getting energy chiefly from dietary fats rather than carbohydrates causes heart disease and other health problems. This view is still held by the majority of those in the medical and nutritional science communities.However, it is now widely recognized that periodic ketosis is, in fact, normal, and that ketosis provides a number of surprising benefits, including neuroprotection against diverse types of cellular injury.
A diet very low in starches and sugars induces several adaptive responses. Low blood glucose causes the pancreas to produce glucagon, which stimulates the liver to convert stored glycogen into glucose and release it into the blood. When liver glycogen stores are exhausted, the body starts using fatty acids instead of glucose. The brain cannot use fatty acids for energy, and instead uses ketones produced from fatty acids by the liver. By using fatty acids and ketones as energy sources, supplemented by conversion of proteins to glucose (gluconeogenesis), the body can maintain normal levels of blood glucose without dietary carbohydrates.
On a high-carbohydrate diet, glucose is used by cells in the body for the energy needed for their basic functions, and about two-thirds of body cells require insulin to use glucose. Excessive amounts of blood glucose are thought to be a primary cause of the complications of diabetes, when glucose reacts with body proteins (resulting in glycosolated proteins) and change their behavior. Perhaps for this reason, the amount of glucose tightly maintained in the blood is quite low. Unless a meal is very low in starches and sugars, blood glucose will rise for a period of an hour or two after a meal. When this occurs, beta cells in the pancreas release insulin to cause uptake of glucose into cells. In liver and muscle cells, more glucose is taken in than is needed and stored as glycogen (once called ‘animal starch’).
Diets with a high starch/sugar content, therefore, cause release of more insulin, and so more cell absorption. In diabetics, glucose levels vary in time with meals and vary a little more as a result of high-carbohydrate meals. In nondiabetics, blood-sugar levels are restored to normal levels within an hour or two, regardless of the content of a meal.
The ability of the body to store glycoge is finite, though. Once liver and muscular stores are full to the maximum, adipose tissue (subcutaneous and visceral fat stores) becomes the site of sugar storage in the form of fat. Given the body’s ability to store fat is almost limitless, hence the modern dilemma of morbid obesity occurs.
Low Carb Diet side effects and dangers
While diet devoid of essential fatty acids (EFAs) and essential amino acids (EAAs) will result in eventual death, a diet completely without carbohydrates can be maintained indefinitely because triglycerides (which make up fat stored in the body and dietary fat) include a (glycerol) molecule which the body can easily convert to glucose. It should be noted that the EFAs and all amino acids are structural building blocks, not inherent fuel for energy. However, a very-low-carbohydrate diet (less than 20 g per day) may negatively affect certain biomarkers and produce detrimental effects in certain types of individuals (for instance, those with kidney problems). The opposite is also true; for instance, clinical experience suggests very-low-carbohydrate diets for patients with metabolic syndrome.
A study of more than 100,000 people over more than 20 years within the Nurses’ Health Study observationally concluded a low-carbohydrate diet high in vegetables, with a large proportion of proteins and oils coming from plant sources, decreases mortality
In contrast, a low-carbohydrate diet with largely animal sources of protein and fat increases mortality!
Many critics argue that low-carbohydrate diets inherently require minimizing vegetable and fruit consumption, which in turn robs the body of important nutrients. Some critics imply or explicitly argue that vegetables and fruits are inherently all heavily concentrated sources of carbohydrates (so much so that some sources literally treat the words ‘vegetable’ and ‘carbohydrate’ as synonymous). While some fruits may contain relatively high concentrations of sugar, most are largely water and not particularly calorie-dense. Thus, in absolute terms, even sweet fruits and berries do not represent a significant source of carbohydrates in their natural form, and also typically contain a good deal of fiber which attenuates the absorption of sugar in the gut. Lastly, most of the sugar in fruit is fructose, which has a reported negligible effect on insulin levels in obese subjects.