young woman exercise
young woman exercise

Yes, it is possible to be thin but unfit! To maintain or increase lean body mass, you need to look at both diet and a comprehensive exercise programme. You’ll not only lose fat, but experience considerable health benefits.

There is a prevailing dogma in the health and fitness industry that deserves serious discussion. We are in an era of ‘thin is fit’, which perhaps stems from the fitness boom of the 1970s and 80s when the mass public of the Western world started running marathons and watching their dietary fat intake. The approach doesn’t appear to have worked particularly well, but nonetheless the increasing struggle with our waistlines has probably added to the perception that ‘thin is fit’.

So how do we become thin and fit? Well, if you follow the trends of the fitness clubs and popular health magazines, you will spend an hour a day on a treadmill or X-trainer and eat low-calorie, low-fat food. The problem is that in the long term, this approach is generally ineffective. Body weight usually drops initially, but stabilises after a while. In an effort to lose more weight, the person may increase the cardiovascular (CV) exercise and further restrict the calories. This may or may not result in ‘thinness’ depending on the individual’s body type, but when you actually measure the percentage of body fat, it is often surprisingly high.


Would you believe me if I told you that many skinny models are actually fat? They don’t look fat, but their body fat might exceed 30% of total body weight, compared with healthy levels of 20 to 25% for women and athletic levels of 15 to 20%. Two slim women could appear the same, but one has a healthy body composition and the other a high percentage body fat plus accompanying health risks.

If you have done your maths, you’ll realise that higher fat mass with the same body weight means reduced muscle mass. There is actually a term for this – ‘sarcopenia’, from the Greek meaning ‘poverty of flesh’. It is usually used to describe the gradual loss of muscle mass as we get older,1 but is entirely relevant to individuals caught in the dieting/exercise cycle.

Of course, people who are outwardly overweight also often have depleted muscle mass and can produce only meagre strength outputs. In comparison, strength-based sport-speople (such as rugby players and weight lifters) often weigh a lot, but are extremely lean because they carry a lot of muscle mass.


If the high-cardio, low-calorie approach doesn’t produce the leanest, fittest body, then what does? Try combining some resistance exercise with CV training, along with appropriate eating patterns for your body type.

Resistance training

Because it increases muscle mass, resistance exercise is thought to raise an individual’s metabolic rate. A meta-analysis and literature review support this viewpoint, showing that resistance exercise is effective in improving body composition, probably because of its ability to increase or maintain lean body mass.2,3 In my practical experience, resistance training, via free weights, machine weights, circuits or core stability training, can be an extremely effective and rapid way of improving body composition.

Cardiovascular training

You may mistakenly think after reading the previous paragraphs that CV exercise leads you into a state of sarcopenia and puts your fat-loss efforts into jeopardy. CV training is in fact often used as the base of a weight-loss programme: the respected American College of Sports Medicine (ACSM)4 recommends progressively increasing exercise to 3 to 5 hours per week. After all, we were designed to move, and traditional workers generally stay lean and fit into old age. The problem comes when caloric restriction is maintained for prolonged periods along with heavy CV exercise – this puts excessive strain onto the adrenal glands, pancreas and liver to support blood sugar levels without adequate fuel intake, and metabolic suppression tends to follow.

What is the optimal intensity at which to do CV training? Fourteen premenopausal untrained women demonstrated that exercise training at 45% of maximum oxygen uptake (VO max) produced greater weight loss than burning the same number of calories at 72% of VO2max, whereas the higher-intensity exercise tended to maintain muscle mass.5


Based on the above theory of fat loss, along with observations, I suggest the following:

  • If you are already quite fit, aim for at least 3 hours of CV training a week (perhaps 2 hours of low to moderate intensity and 1 hour of high intensity) and at least 1 hour of resistance training a week (two 30-minute sessions).
  • If you are starting from a low fitness base, the most appropriate approach may be to start with a low-intensity exercise such as walking. In this way, the programme will be achievable, doesn’t require specialised equipment, and may be more successful than a formal exercise approach: compliance with exercise referral programmes can be as low as 31%.6 Overweight individuals should aim to accumulate an hour of low- intensity exercise most days,7 and tools like step counters and activity diaries may be helpful to boost adherence. Resistance-based exercise can be done by anyone and you can choose from formal weight training, super-circuits (available in most gyms) or Pilates and tone classes. The basic requirement is to use large muscle groups in a repetitive way until some fatigue is felt.

In addition, your exercise experience must be enjoyable. Activities such as dancing, swimming, cycling and exercise classes can be shared with family or friends. In addition to planned exercise sessions, spontaneous minor activity can account for 20% of the differences in energy expenditure in a 24-hour time frame.8 General activity such as housework, gardening, walking to the shops and taking the stairs instead of the elevator can be extremely cumulative.


I have never helped an individual towards a ‘lean and mean’ body shape without some attention to their food intake. The fat-loss effects of exercise can be potentiated by the addition of an individual meal plan. For example, a meta-analysis of 493 studies showed weight lost through exercise, diet or diet plus exercise to be 2.9, 10.7 and 11.0 kg, respectively, for the period of study.9 At follow-up after a year, diet plus exercise tended to be the superior programme, possibly owing to maintenance of muscle mass.

For an effective ‘fit, not fat’ programme many components of health should be considered. A comprehensive exercise programme that maintains or increases lean muscle mass should certainly be an integral part of your plan. In addition to potentiating fat loss, you are likely to experience considerable health benefits.


  1. Marcell TJ. Sarcopenia: causes, consequences and preventions. Journal of Gerontology 2003; 58A(10): 911-916.
  2. Ballor DL, Keesey RE. A meta-analysis of the factors affecting exercise-induced changes in body mass, fat mass and fat-free mass in males and females. Int J Obes 1991; 15(11): 717-726.
  3. Votruba SB, et al. The role of exercise in the treatment of obesity. Nutrition 2000; 16(3): 179-188.
  4. Jakicic JM, et al, American College of Sports Medicine Position Stand. Appropriate intervention strategies for weight loss and prevention of weight regain for adults. Med Sci Sports Exerc 2001; 33(12): 2145-2156.
  5. Mougios V, et al. Does the intensity of an exercise programme modulate body composition changes? Int J Sports Med 2006; 27(3): 178-181.
  6. Hillsdon M, Thorogood M, A systematic review of physical activity promotion strategies. Br J Sports Med 1996; 30(2): 84-89.
  7. Leermakers EA, et al. Exercise management of obesity. Med Clin North Am 2000; 84(2): 419-440.
  8. Dauncey MJ. Activity and energy expenditure. Can J Physiol Pharmacol 1990; 68(1): 17-27.
  9. Miller WC, et al. A meta-analysis of the past 25 years of weight loss research using diet, exercise or diet plus exercise intervention. Int J Obes Relat Metab Disord 1997; 21(10): 941-947.
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