Food, Nutrition and Weight Loss

Food, Nutrition, and Weight Loss[icon name=”user” class=”” unprefixed_class=””]  Dr. Swapnali Halder


Food that we eat gives us nutrients and calories1, the vital components to keep us alive. Nutrients are the substances in the food that nourish the body for growth and maintenance. Nutrient enriched food is important to maintain a healthy body. Our food contains macronutrients such as carbohydrate, protein, fat and fibers, and micronutrients such as vitamins and minerals. Calorie is defined as the unit of energy supplied by food. Amount of calories vary by food types ie., carbohydrate, protein, fat and fibers have different calorie levels. I should be noted that calories comes not only from the food, but from tbeverages as well.


Our body breaks down carbohydrates to glucose unit, which is used as fuel to generate ATP (adenosine triphosphate). Bread, starch, grains, cereals, food with added sugar, vegetables like potato, and various sweet fruits are common sources of carbohydrates. Carbohydrates are classified as simple carbohydrates and complex carbohydrates. The basic unit of carbohydrate is called monosaccharide. Simple carbohydratesare composed of one or two monosaccharide molecules, for example, glucose, fructose, sucrose, lactose etc.

Simple carbohydrates are broken down to glucose faster than complex carbohydrates, thus help raise blood glucose levels quicker. Fruits are rich in fructose and sucrose, whereas lactoseis found in milk. Carbohydrates that contain three or more monosaccharide units are called complex carbohydrates. Starch containing foods, bread, potato, grains that are slowly degraded to glucose, belong to the group of complex carbohydrates. After usage in the energy production, excess of the consumed glucose is stored in the liver and muscles for future use.

Another major component of food is protein, which is comprised of amino acids. Out of twenty standard amino acids that serve as building blocks of proteins, eleven amino acids are synthesized in the human body. However, the remaining nine amino acids, called essential amino acids, though required for maintaining normal functions of the body, are not synthesized in our body. These essential amino acids include histidine, methionine, valine, lysine, leucine, isoleucine, phenylalanine and tryptophan, and must be supplied from the diet. Animal meat, poultry, fish, milk and dairy product, egg, beans and peas, tofu are great sources of proteins.

Fat intake is important for maintaining health of the nervous system. Dietary fats come from animal fat, oil, egg yolk, nuts, milk, cheese, butter and other milk products. Fats are composed of fatty acids and are assembled in different varietiessuch as trans fat, saturated fat, cholesterol, monounsaturated fatty acids (MUFA) and polyunsaturatedfatty acids (PUFA).Regular consumption of trans fat and saturated fats are associated with increased risks of coronary heart diseases. On the contrary, omega-3 and omega-6 poly-unsaturated fatty acids are believed to decrease risks of those heart diseases.

Dietary fibers or roughages are indigestible part of complex carbohydrate that facilitatebowl movements.Whole grains, cereal brans, lentils, dry beans and peas supply fibers in our foods. Studies have shown that high intakes of dietary fiber may lower risk for developing coronary heart disease, stroke, hypertension, diabetes, obesity, and certain gastrointestinal diseases 2.

Vitamins include vitamin A, D, E, K, B, and C, first four of which are fat-soluble and other two are water-soluble. Fresh fruits, vegetables, egg, fish oilsare best sources of vitamins. Water-soluble vitamins cannot be stored in the body as they are quickly excreted though urine. Vitamin A is important for good eyesight, vitamin D and calcium maintain bone health3.

Vitamin E is enriched with antioxidant properties that might be essential for prevention against coronary heart disease, cancer, eye disorder etc4.Vitamin K maintains blood coagulation factors, prevents hemorrhage, and also helps maintain bone health5.  There are several vitamins that fall under the B group, such asB1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folic acid), B12 (cobalamins).

Together they are referred to as vitamin B complex. Vitamin B complex contributes to wide range of health benefits including blood cell production and prevention of anemia, production of stress hormone, preventing neurological birth defects etc. Vitamin C gives protection from common cold and bleeding gum.

Some vital minerals are potassium, calcium, magnesium, iron, zinc, selenium etc.3 which play vital role in maintaining a healthy heart, healthy bone and nails, preventing osteoporosis and anemia etc. Seafood, meat, leafy vegetables, milk, cereals, beans are good sources of minerals.Vitamins and minerals, obtained either from food or supplements,do not provide calories, however they help in conversion of food to energy, keep our systems healthy and protect us from developing various health issues.


Balanced diet is a diet that contains right proportions of carbohydrate, protein, fat, fibers, vitamins and minerals and meets the daily requirements of these nutrients.For adult human being 45%-65% of his or daily energy source should come from carbohydrates whereas 10%-30% is allotted for proteins6. An adult’s daily consumption of fat should be limited to 20%-35% percent of total calories6. Daily recommendation for fiber intake is 14g/1000 Kcal, i.e, 28 g for 2000 kcal diet2.

Both excessive of any nutrients and scarcity of any of these nutrients may hamper normal functions of the body in the long run.  Therefore, in our daily diet, we need adequate amount of carbohydrate for energy production, protein for maintaining muscle mass, fat for healthy nervous systems, vitamins and minerals for proper absorption and metabolism of food and for immunity. However, excessive carbohydrate consumption may increase blood glucose levels and may be associated with unhealthy weight gain or diabetes.According to some research studies, chronic intake of high amount of animal protein may increase risk of cancer in the gastrointestinal tract.Consumption of too much fatty or oily food increases risks of cardiovascular diseases and obesity.

Therefore a balanced diet is really plays an important role keeping us healthy.


Excess abdominal fat carries risks of diabetes and heart diseases. Men with waist size bigger than 40 inches and non-pregnant women with waist size more than 35 inches must pay attention in loosing weight7. A body mass index (BMI) greater than 25 also indicates that a person is overweight7.

Even if you are maintaining a healthy body weight, make sure that your diet has enough fruits, nuts, vegetables and whole grains that are packed in nutrients and are critical to maintain a healthy and fit body. A balanced diet can be vegetarian, non-vegetarian, or even vegan as long as all the different nutrients are included in the required amounts.


Vegetarian people consume only plant-based and dairy-based food, but excludeanimal or bird meat, seafood and eggs from their diet. Non-vegetarians typically do not have such food restrictions and consume both plant-based and animal-based food products. A vegan diet is totally based in plant products. Since vegan and vegetarian diets have a substantial amount of carbohydrate, care should be taken to make sure that the people whofollow those diet patterns receive adequate proteins as well.

For average people with normal physical activities, daily protein requirement is 0.8 g/kg body weight, however a recent research suggested that ≥1.0 g/kg body weight protein intake might be helpful for achieving optimal metabolic health8. Vegans can meet their daily dietary protein requirements by including beans and soy-protein containing food and beverages such assoy milk, margarine, enhanced bread, soy containing burgers, powdered isolate, dairy-free cheese etc9.

Milk protein casein, and whey protein can also be considered as alternative protein sources for vegetarians.People also opt for protein supplements or fortified foods if sufficient protein is not obtained form one’s diet.


Balancing calorie is the key to maintain a healthy body weight. In simple words, it means using approximately same number of calories as you are consuming. Consuming extra calories that the body uses leads to weight gain, and the opposite of it leads to weight loss1. The amount of calorie the body would use is partly dependent on the body’s metabolic pattern and the level of physical activity.

To lose one pound (lb) body fat, one needs to cut down 3500 calories from one’s calorie requirement. That means 3500 calories over our body’s requirement make us gain one pound. Cutting down ~500 calories from the daily diet may help loosing 1lb weight per week1. So what we eat is as important as how much we eat.


Appetite control is a way of loosing extra body weight where the strategy is to decrease the energy intake than its expenditure.Studies have shown that vegetarian and meat-based high protein weight loss (HPWL) diet have similar effects on appetite and weight loss in over-weight but otherwise healthy men 9. Meat-based high protein weight loss diet helps reduce food intake in a 4 weeks study period10.

Both soy-protein based and meat based HPWL diet improve overall health condition by lowering blood glucose, triglyceride, and LDL cholesterol (i.e, bad cholesterol) levels 9.

However relying totally on a diet that contains mostly animal proteins and very low carbohydrates and fibers may pose a threat of cancer if consumed for longtime,since this diet creates some hazardous metabolites in the gut.Therefore a vegetarian HPWL diet could be a healthier alternative for people who want to follow HPWL diet to loose weight.

The 2010 Dietary Guidelines for Americans provided recommendations for achieving and maintaining healthy weight through healthy eating habits, where the strategy is to follow a weight loss regimen by decreasing calories while maintaining sufficient nutrient intake, and increasing physical activities 11. One simple way to cut-down the calories is consumption of low-carbohydrate and low-fat foods.


Changing the proportions of different macronutrients in the diet may impact hunger and satiety, as the research suggests10. Though there is no ideal definition of low-carbohydrate diet, a daily carbohydrate intake below the recommended 45% by the Dietary References Intakes of the Institute of Medicine8 could be considered as a low-carbohydrate diet.

Replacing deep fried, sautéed or creamed items with baked, grilled or steamed items may help reduce fat contents from one’s plate.


Loosing weight is an important fitness strategy for obese people to follow, however weight loss is associated with loss of bone density, particularly in post-menopausal women 12,13.

Therefore women should be more cautious about their weight loss regimens and take measures to maintain bone-density while loosing excessive body fat. A balanced dietary pattern accompanied by increasing physical activities through regular exercises is the secret to stay healthy, energetic, and maintain healthy body weight irrespective of one’s age and sex.

Research has shown that 45 minutes brisk walking thrice a week improves ideal body weights and stress levels in moderately obese (BMI 29-35 kg/m 12) post-menopausal women 14. In addition to weight loss, regular brisk walking helps improve overall fitness and lipid profile in post-menopausal women15.

Swimming has been proven to be another effective method of reducing body fat16. Incorporating resistance training in one’s fitness routine is helpful inreducing body fat as well as improving muscle powerin both men and women17. Lastly, for people who are interested in light to moderate intensity exercises, yoga could also serveas a potential therapy for weight loss and healthy weight maintenance 18.


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