Diet by Karanika Mahindra

Energy restriction through intermittent fasting (IF) has become popular among people as a means of weight control. Run a Google search and IF seems to be the best diet for quick results. It promises “weight loss” in a short span of time.

What is Intermittent Fasting ?

Intermittent fasting comes under the umbrella term of Intermittent Energy Restriction (IER). This, by principle, involves prolonged periods of starvation or fasting between meals which creates an energy deficit (or calorie deficit) in the body.

Why it doesn’t work ?

All cells, tissues and organs in the body, including our brain, need a constant supply of fuel. The body needs a regular supply of energy to function and think.

Crash diets like IF take toll on water reserves and electrolyte balance of the body. Restricted consumption of timely and balanced meals leads to depletion in salt and magnesium stores in the body. To make up for this loss, sodium is pulled from bones into the bloodstream leading to loss of bone mineral density.

Not eating meals at regular intervals of 2-3 hours causes a rise in the body’s cortisol levels. Cortisol is a stress hormone and has a major role to play in regulating metabolism and blood sugar. High levels of cortisol in the body, paired with irregular meals and long gaps leads to a) Increased Fat Storage and b) Muscle Breakdown. Additionally, a spike in body’s cortisol levels limits body’s natural defense mechanism and lowers immune system function. 

Energy deficit in diet causes the body to believe that there is going to be prolonged starvation. As preparation, the body then enters a state of stress. In such a scenario, everything we eat is converted to and stored as fat. During periods of starvation, glycogen stored in muscles becomes the primary source of energy. Exercising and heavy activity during the fasting window causes further breakdown of the muscle.

Hence, the reduction in weight during IF is essentially loss of “Lean Body Weight” (muscles mass and bone mineral density) and not “Fat Loss”, like we would want to believe. The weight you gain back is all fat. Post IF the total percentage of fat is higher than what it was when you started off !

Health Effects of IF:

Spells of marked energy restriction disturb the hypothalamic-pituitary-gonadal axis in women. This alters the frequency and length of menstrual cycles and cause menstrual discomfort (cramps, headaches, bloating etc.).

Another hypothesis under scrutiny is that bouts of starvation followed by binging decrease the brachial artery flow mediated dilation which could increase risk of atherosclerosis and hypertension in the long run.

There is ample evidence to suggest that an erratic eating pattern of starvation and binging leads to:

Limitations to the research data available:

1. Most study trials are conducted for a short duration of only few weeks. Moreover, till date no study has included a true follow up period leaving open the question – whether IF is a durable (weight loss) strategy over longer periods of time. 

2. The studies are only weight loss oriented and do not take into account, the more important aspect of – body composition and metabolic parameters of health and fitness. 

References:

1. Berg et al., 2002
2. Harvie and Howell, 2017
3. Rynders et al., 2019