DoctorSpeak: Why over-exercising can be harmful if you are obese

Anshul (16) had pain and stiffness in his left leg. He had no history of trauma. The obese teenager (body mass index 42) had been jogging daily for an hour for the past two months to reduce weight. Initially the pain was mild, but had worsened since the last five days. Examination and MRI revealed that he had stress fracture on his shin bone. He had to use a knee brace for two months and stop exercising to let his fracture heal.

Priya (35) had been experiencing pain in both her knees for the past two years, but it had worsened in the last two months. In order to lose weight, Priya (BMI 38) had been using treadmill for the past three years for at least 45 minutes every day. Examination and MRI of the knees revealed that cartilages were thinning out with signs of injury on both knees. These changes were irreversible. Priya was advised to modify her exercise routine switching from treadmill to cycling/ cross-trainer machine.

In both the cases, the knee joints were not able to take the load because of the excessive body weight, and the long duration of unsupervised exercise only aggravated the issue causing injury to the joints.

Excessive load on the skeletal system is only one of the challenges being faced by the obese. Overweight or obese (BMI 25 or above) people are at an extremely high risk of having diabetes, hypertension, heart diseases, osteoarthritis of joints, sleep apnoea and respiratory problems, and certain cancers — such as breast, colon and endometrial cancer.

According to National Family Health Survey-5 (2019-21), approximately 24 per cent people in India are obese, and the numbers are rising alarmingly because of a sedentary lifestyle, a diet high in processed food and lack of exercise.

In most cases, when weight increases alarmingly, most people are advised to lose weight on medical grounds. Many people start exercising excessively or strenuously for long periods but without adopting good dietary habits. Most such cases lead to injuries due to overload on the musculoskeletal and the cardiovascular systems because of sudden and long duration of strenuous physical activity.

The increased body mass/ larger surface area of an obese individual demands more oxygen and nutrient delivery during physical activity. To meet this demand, the cardiovascular system compensates by increasing the heart rate that results in putting more load or stress on the cardiac system.

Additionally, obesity is frequently associated with comorbidities such as hypertension, dyslipidaemia (abnormal lipids/fat levels in the blood) and noncompliant vessels (stiff, hardened vessels unable to expand and stretch easily in response to changes in blood pressure) which raise the peripheral vascular resistance and thus further burden the heart. Over time, this can contribute to left ventricular hypertrophy (thickening of a heart ventricle’s walls, often a response to the heart working harder than usual), reduced exercise tolerance, and, in extreme cases, an increased risk of sudden cardiac arrest during aggressive physical exertion.

Apart from cardiovascular stress, extreme physical activity by obese people imposes disproportionate mechanical load on bones, joints, muscles, and ligaments. Body weight acts as an external load on the lower limbs, and during activities like running, jumping, or resistance training, this load multiplies several times. For example, the knee joint may experience force up to three to four times the body weight during walking, and even higher during more strenuous activity.

Obese people are, therefore, more susceptible to joint degeneration, cartilage wear, and problems like osteoarthritis, especially in weight-bearing joints like the knees, hips and ankles. The muscles and ligaments, tasked with stabilising these joints, also experience enhanced strain. Micro-trauma or repetitive stress can result in overuse injuries, tendonitis, or ligamentous sprains. Moreover, the reduced muscle-to-fat ratio in obesity limits muscular endurance, making tissues more vulnerable to load failure under aggressive physical challenges.

Thus, aggressive unsupervised physical activity — often undertaken in gyms or outdoor training — can precipitate acute injuries in obese persons. The combination of excess body mass and sudden mechanical loading can exceed the tolerance of musculoskeletal tissues, leading to stress fracture or ligament tears.

Obesity is a complex condition that cannot be addressed by a single intervention. A three-pronged approach of diet, physical activity, and controlled/supervised exercise offers a practical, evidence-based strategy to manage and prevent obesity.

— The writer is Chairman, Orthopaedics, Joint Replacement and Sports Injuries, Paras Hospital, Panchkula

Three-pronged approach to control obesity

This is a widely accepted model which consists of diet changes, general physical activity, and controlled/supervised exercise.

DIET

Caloric Deficit: The primary dietary principle in weight management is creating a moderate calorie deficit. A daily reduction of 500–750 kcal can result in safe and sustainable weight loss of 0.5–1 kg per week.

Balanced Nutrition: Crash diets or highly restrictive regimens often fail in long term.

Macronutrient Quality: Diets low in refined sugars, saturated fats are suggested, and high protein and fibre-rich foods including whole grains, lean proteins, fruits, vegetables, legumes, nuts and healthy fats are recommended.

PHYSICAL ACTIVITY

Walking, climbing stairs, household chores, gardening, etc. should be included in the daily activities.

Checking sedentary habits with small but frequent bouts of activity enhances basal metabolic rate and overall energy balance.

CONTROLLED AND SUPERVISED EXERCISE

While general physical activity is beneficial, structured exercise under supervision is critical for obese individuals who face heightened musculoskeletal and cardiovascular risks.

Cardiovascular Training: Brisk walking, swimming, cycling, or treadmill workouts improve heart health, endurance and fat oxidation.

Resistance Training: Strengthening muscles increases basal metabolic rate, aiding

long-term fat loss.

Progressive Overload: Structured programmes allow gradual increase in intensity, ensuring adaptations do not overwhelm the body.

FACTCHECK

India has the third largest obese population in the world after the USA and China, as per WHO estimates. The NFHS-5 (2019-21) reported that 6.4 per cent Indian women and 4 per cent Indian men (15-49 yr) were obese. The survey also showed a significant increase in overweight children under 5. The NFHS-5 introduced for first time the abdominal obesity measurement, which is quite high in India — 40 per cent women and 12 per cent men are abdominally obese, but measured on BMI, only 23 per cent women cross the cut-off mark for obesity.

Source: NFHS-5 (2019-21)