
What whistles touch fruits and vegetables on a diet?
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How eating fruits and vegetables affects the body when following a low-carb diet
When we think about dieting, we think about eating healthier and therefore consuming more fruits and vegetables. However, in order to lose weight, stored fat or reduce potential diseases as a result of high sugar levels, most fruits inhibit the efforts that a person makes for any of these purposes.
Today I'll explain why fruits and other vegetables, even more than other carbohydrates like pasta, potatoes, bread or rice, can slow down or completely stop your dieting efforts. I'll also show you which fruits may be acceptable in very moderate amounts so as not to disrupt the process and which vegetables you can safely consume when it comes to controlling blood sugar, eliminating fat stored in the body or losing body weight.
Fructose and glucose: what does our body read when we consume them?
Sugar metabolism occurs when the energy contained in the food we eat is converted into fuel for the body. The body's cells can use glucose directly for energy, and most cells can also use fatty acids or fat for energy, provided that glucose is not available.
Fructose, glucose, sucrose, galactose… all words that end in this infer that they are sugar of some kind and that once digested they will pass into the bloodstream in the form of glucose, which is the only brand our body knows. But be careful! Not all sugars are the same.
Glucose and fructose are metabolized differently:
Blood glucose stimulates the pancreas to release insulin and the cells (in any part of the body) can capture this glucose to obtain the energy necessary to carry out all the daily activities that we propose. After this, glucose returns to normal levels, but insulin will have deactivated the use of fat for this purpose since it has given priority to glucose. In addition, the glucose that has not been used for this purpose will be stored in the form of glycogen in the muscles and in the form of lipid in the fatty tissues of the body.
Glucose goes everywhere in the body
Fructose also enters the bloodstream from the intestine, but it first goes to the liver, which pre-processes it to see if it becomes glucose or fat. The liver can eventually release glucose and fat into the bloodstream or store it in glycogen or fat deposits.
The big difference:
Remember that ketones (energy produced in the absence of glucose) are produced in the liver, so anything that affects the liver is going to have an impact on ketone production.
Glucose is used by virtually every cell in your body, including your brain, whether you are in ketosis or not. Every cell has the ability to use glucose.
Fructose is metabolized in a very different way, since the liver is the only organ that can process and metabolize it. Fructose cannot be used by all the cells in the body and, in addition, its presence completely inhibits the production of ketones, which, as mentioned above, are produced in the liver.
When we consume carbohydrates that do not come from fruits, the liver only captures 20% of the entire glucose load, while when we consume fruit the liver captures 100% of the entire sugar load.
As for the restoration of what is called liver glycogen, it is much easier to store carbohydrates from fruit in the liver than from other carbohydrates (pasta, bread, etc.).
Since glucose can be used by all cells in the body, when we consume glucose we have the ability to burn it faster. But since the body cannot use fructose because it is occupied by the liver, when we consume it and do not use it in physical activity, it tends to be converted into free fatty acids and triglycerides and, finally, into fat.
So when we consume carbohydrates, our body absorbs glucose, that is, simple sugars that come from carbohydrates, and chains them into a formation called glycogen to then store them in the musculoskeletal system and a little of it in the liver. The interesting thing is that muscle tissue does something different with the glycogen stored there: it only uses it when we are making a physical effort and/or need physical energy for some activity.
Glycogen, which acts as a glucose store in the liver, has the function of maintaining normal blood sugar levels. When the body's glycogen stores are depleted, the breakdown of body fat (mainly triglycerides) results in increased availability of fatty acids and the production of ketones, but the liver needs to be almost or completely devoid of glycogen to produce them.
However, even though we are in ketosis, muscle glycogen levels are still elevated and we are not tapping into them unless we are doing strength exercises such as weight lifting or high intensity interval training where the muscles convert glycogen into glucose for immediate use. This is why eating fruit may be preventing you from achieving the desired effects of your diet.
It should be clear that fructose is mobilized through a process called “facilitated diffusion” where a different transporter than glucose is used to enter enterocytes (cells in the intestine that absorb nutrients and secrete protein). When you consume fructose, it goes directly to the liver when digested, while glucose goes throughout the body.
Both carbohydrates and proteins trigger an insulin response.
There is a big difference between a food that increases blood sugar (or has a high glycemic load) and foods that only trigger an insulin response.
When we consume sugar, insulin is produced naturally and the pancreas needs to produce this insulin so that the sugar in the bloodstream is absorbed by the cells in the part of the body where it needs to be used. The problem with a person who has diabetes is that they do not produce the necessary insulin and this sugar remains floating in the blood.
Now, it turns out that it is not only by consuming carbohydrates that we stimulate insulin production. Protein is considered one of the most insulinogenic foods (it improves insulin sensitivity). In fact, a 2005 study found that consuming a protein (in this case whey) before eating the rest of your meal produced an insulin response by lowering blood glucose, meaning that thanks to insulin, glucose could be absorbed better. [1] Further studies indicate that consuming isolated pea protein half an hour before your first meal (if you are doing intermittent fasting or breaking your fast) can be very effective not only in lowering blood sugar but also because it has no inflammatory effect.
Fruits and vegetables that do not alter blood sugar levels
If sugar comes with its inherent fibre (as whole fruit does), up to 30% of this sugar will not be absorbed. Instead, it will be metabolised by microbes in the gut, which can improve microbial diversity and help prevent disease. Fibre will also result in a slower rise in blood glucose, which has been shown to have positive health effects.
Avocado = Avocado is a fruit and although its fat content is high, it also contains minimal fructose. So it is recommended not to eat more than 1 avocado per day.
Blackberry = 7 grams of sugar per cup not including fiber so it is recommended for a low carb diet around ½ cup (70 grams) which would contain 4 grams.
Raspberry = they have a high fiber content which allows them to be metabolized slowly. It is recommended to consume ½ cup (60 grams) which contains 3 grams of carbohydrates.
Strawberries = They are high in fiber, but also water, so up to ½ cup a day is safe to avoid altering blood sugar. In addition, strawberries promote the production of adiponectin and leptin, two hormones that stimulate the oxidation of fatty acids, or better yet, help burn fat.
Blueberries = half a cup (75 grams) contains 9 grams of carbohydrates.
Cherries = Half a cup of cherries (75 grams) contains 8 grams of carbohydrates.
Vegetables
The vegetables with the lowest carbohydrate content, with less than 5 grams per 100 grams of weight, are:
Spinach
Green zucchini
Lettuces
Cucumber
Cabbage
Asparagus
Kale
Celery
References
[1] Frid, A. American Journal of Clinical Nutrition , July 1, 2005; vol 82: pp 69-75.