Nutrition Meets Food Science

“Depreciate those Extra Calories” -Go with the best diet…


While planning weight loss, which diet to go with- low carb or low fat? Do they cause side effects? What if it leads to nutrient deficiency? What will happen after discontinuing diet? All these are common questions arising in our mind when we are ready to choose between the two most trending diets- Low Carbs and Low Fat Diets. Let’s understand it a little deeply today.

Before choosing any diet it is important for a dieter to have basic knowledge of macronutrients – their role & requirements in body, so that you can check, compare & ensure yourself with nutrient sufficiency for whichever diet you start up.

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Carbohydrates are either simple or complex & are major sources of energy coming from the diet. In India, 70-80% of the total calories come from Plant based sources of carbohydrates. A diet rich in Complex carbohydrates such as beans, pulses, whole grains & vegetables are rich in dietary fibre which delays emptying of food in stomach. It also decreases the levels of lipids & cholesterol in the blood whereas increases bulk of the stools. So, even if you choose a diet low in carbs, make sure you include more of complex carbs over simple one for better weight loss results.

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For a healthy adult, about 1900-2300 kcal of energy is required by the body to carry out normal functioning which majorly comes from carbohydrates.


Proteins are complex molecules composed of amino acids; as essential amino acids are not synthesized by our body it needs to come from the diet. Both low carb as well as low fat diets are planned as protein rich in order to meet the energy demands & perform sparing actions.

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Generally, proteins are recommended to be around 55-60 gm/day for an adult with ideal body weight.


Fats serve as fuel for our body providing 9 kcal of energy per 1 gm. Under normal diet, 20-30 gm of visible fat are recommended for an adult women whereas 25-40 gm for adult man.

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The acceptable macronutrient distribution ranges (AMDR) set forth by the Institute of Medicine of the National Academies recommend that people get:

  • 45–65% of their calories from carbs
  • 20–35% of their calories from fats
  • 10–35% of their calories from proteins

Understanding Low carb & Low fat diets

People usually get confused in understanding the difference between low carb & low fat diets. Although they serve same purpose of losing your body’s weight but are quite different from each other.

Low Carb diet

A Low carb diet involves limiting your daily Carbohydrate intake up to certain % or gm per day & is differentiated on the basis of % of daily Carbohydrate intake as:

  1. Very low carb diets ( also known as Ketogenic diet) : less than 10% of total daily calories, or 20–50 grams per day on a 2,000-calorie diet
  2. Low carb diets : less than 26% of total daily calories, or fewer than 130 grams per day on a 2,000-calorie diet
  3. Moderate carb diets : 26–44% of total daily calories

Issues of Concern

Several health concerns are associated with long term following of low carb diets that needs to be addressed.

  • It may induce Nutritional ketosis (a metabolic state in which your body uses fat for energy instead of carbs).
  • Prolong following very low carb diet may impair cardiovascular, lipids & renal functions. However, there is no clear evidence that very low carb diet produces metabolic keto-acidosis.

Low Fat Diet

As the name suggests, here the amount of fat you eat is restricted to less than 30% of the total daily calories.

Fats when oxidised produces higher no. of calories than any carbohydrate or protein so reducing fat from diet can help to reduce overall calorie intake. But it is important to remember that fats also play significant role in our body, one should not at all aim for a no fat diet.

Evidence Based Comparison

Much Research concludes that low carb diet is more effective for short term weight loss than low fat diet. However, several researchers suggest that both low carb as well as low fat diet have similar effects on weight management.

According to a 6 month older study conducted among 132 obese participants, it is observed that participants following low carb diet tend to decrease weight 3 times more than those who followed low fat diet. In People living with diabetes, it is seen that low carb diet & low fat diet have almost similar effects on weight changes. It is better concluded with choosing a balanced nutrient sufficient diet & sticking to it for longer period will result in successful weight loss & better health. Low carb diet also has better result in reducing belly fat as well as total fat mass than low fat diet.

In an another study, a low carb, high protein diet decreases feeling of hunger, giving you satiety for longer period & also improves mood as compared to low fat diet.

On the other side, a low fat diet may decrease your body’s Peptide YY hormone levels (Peptide YY is a hormone produced in intestine & functions in reducing appetite hereby limiting your food intake).

Effects on Blood Sugar levels:

  • High carb diet can lead to sudden spike in blood glucose level which may be harmful for the body; henceforth following a low carb diet (less than 45gms per day) will help to regulate blood glucose level under normal range.
  • One study on 56 people with type 2 diabetes reveals that low carb diet is really effective for weight loss, requires less insulin injections & majorly helps in controlling blood sugars.
  • Another small study in 31 people was done comparing effects of both the diets & found that low carb diet works well in reducing levels of circulating insulin & thereby promotes insulin sensitivity.
  • Also, Low carb diet promotes HDL (good) cholesterol & decreases triglycerides than Low fat diets.

Both the diets helps in regulating short term high blood pressures; however more research is needed to know their long term effects on overall health.

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Hence, both the diets show effective results for short term weight loss, with low carb diet being more promising for greater short- term weight loss. Mantra for long term weight loss is just sticking to a well balanced diet for a healthy life. Any changes in diet for weight loss should be done in consultation with doctor, especially for diabetics.

(Adapted from Health Line Magazine)

Abir Ansari

Jr. Nutritionist, PFNDAI

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