How Severe Weight Loss Really Affects Female Bodybuilding

The Cost of Dieting Down for Fitness Women

Body fitness competition
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Clinical studies often examine weight loss surrounding the obesity epidemic. Of course, this type of research is necessary given that 30 percent of Americans are obese with declining health. But what about active women who are normal weight involved in fitness and bodybuilding? 

Normal weight athletic women feel that the health implications of dieting down is an important subject just as worthy of clinical research. They want to know what happens to their body with severe weight loss and low body fat. Is it safe? Many questions and concerns for these women have been left unanswered until now.

Finding reliable information for females who desire to lose weight for competitive purposes is a difficult process. According to expert reviews, studies are lacking and what’s out there is dated material of poor quality.

Researchers have taken the time to examine the effects of severe weight loss on active female fitness competitors. They specifically address changes in body composition and hormone function over a three to four-month dieting down period.

Research suggests that dieting during competitive bodybuilding has some positives as well as some negatives.

  • Dieting led to minimal muscle loss

  • Most dieters experienced overall fat loss

  • Muscle function was maintained

  • Leptin and estrogen levels normalized during recovery

  • Dieting affected hormone function

  • Testosterone levels dropped

  • Thyroid hormone levels were affected by weight loss

  • Other unknown long-term effects

The Research

Recruitment for the study was narrowed to 50 healthy young women who were International Federation of Bodybuilding and Fitness (IFBB) amateur fitness competitors. The volunteers were divided into two groups of 27 women dieters and 23 control participants. The duration of the research was broken down into the following categories typical of contest preparation.

2 Phases of Contest Preparation

  • Dieting down or cutting phase (approximately 20 weeks): The dieting group decreased calories by 30 percent and modified exercise. The control group maintained both nutrient intake and exercise.
  • Recovery phase (approximately 19 weeks): The dieting group increased calories back to original baseline levels. The control group maintained both nutrient intake and exercise.

All women underwent extensive lab work and clinical body scans prior to and upon completion of the study. Fitness assessment testing included DXA scan, bioimpedance, skinfolds, blood pressure, and muscle strength measurements.

The competitors had a strong resistance training background and trained in their own programs during the study. The diet group participants followed split routine workouts often used by bodybuilders. Split routines focus on single muscle groups per workout session. Training sessions lasted between 40 and 90 minutes. The participants also practiced posing routines as part of their training.

Aerobic training consisted of either high-intensity interval training (HIIT) or low to medium intensity running/walking. HIIT routines lasted approximately 20 minutes and lower intensity aerobics typically 30 to 60 minutes. All participants refrained from HIIT exercise during competition week and used only lower intensity aerobics. The majority of the women preferred separate cardio and resistance training so they completed two differing workouts daily.

Daily nutrition intake for the control group remained the same while the dieters reduced total caloric intake by almost 30 percent. The largest reduction was in the form of carbohydrates for the diet group. Before dieting down, the diet participants consumed approximately 215 grams of carbs daily and reduced to 126 grams daily. This value was increased slightly above baseline (229g daily) during competition week in an attempt to replenish muscle glycogen stores. Adding carbs back into the diet gives the muscle tissue a fuller look as water is returned to dehydrated tissue.

Protein intake was approximately 185 grams per day and fat consumed was around 53 grams daily during the dieting phase.

Caloric Intake During the Study

According to the study, total energy (caloric) intake for the diet group could be broken down like this:

  • Pre-diet phase: 2244-2400 calories
  • Diet phase: 1700-1800 calories 
  • Recovery phase: 2043-2300 (returning to baseline or pre-diet levels)

Workout intensity and duration remained constant for the control group. However, the diet group implemented varied training intensity or duration depending on dieting phase. Typically, fitness competitors utilize a tapering off period during competition week. This simply means competitors reduce, alter or eliminate normal workouts in an attempt to improve the aesthetics and strength of their body. The diet group reduced their time resistance training and increased weekly aerobic sessions during the research period.

Research Results

What did researchers find and how does severe weight loss affect a female fitness competitor or bodybuilder?

Research results indicated the diet group was able to successfully reduce body fat mass and overall body fat percentage. Body fat percentage for all participants returned to baseline or original values during the recovery phase. Body composition was measured using three different methods and the following was reported for body fat percentage:

  • DXA scan - 23.1 reduced to 12.7 percent (considered the most accurate body composition test)
  • Bioimpedance – 19.7 reduced to 11.6 percent
  • Skinfold calipers – 25.2 reduced to 18.3 percent

Another positive finding was diet not significantly affecting lean mass according to DXA scan results. However, measurements using bioimpedance, skinfolds, and ultrasound did show a slight decrease in muscle mass.

On average, the results found that all competitors having a significant decrease in fat mass and most of them a slight decrease to no change in lean muscle.

Isometric and explosive leg strength was maintained during the diet phase for both groups. However, dieting did show a decrease in strength for bench press compared to the control group.

Hormone function results were not as positive for the dieting women. Blood tests revealed decreased leptin, testosterone, and estradiol for those dieting compared to the control group. Leptin hormone helps regulate energy balance, fat stores, and signals satiety when we eat. Testosterone and estradiol are the primary sex hormones controlling male and female characteristics.

Decreased sex hormones, especially estradiol (estrogen) caused many of the dieting women in the study to experience menstrual irregularities or amenorrhea (no period). Leptin and estradiol levels did return to normal during the recovery phase but unfortunately, testosterone remained below normal values. Low testosterone in women can adversely affect sexual health, libido, energy, and mood. 

Thyroid stimulating hormone (TSH) levels remained in the normal range but T₃ (triiodothyronine) was decreased for the dieting group. T₃ is produced by the thyroid gland and low levels may indicate hypothyroidism or starvation. This hormone plays an important role in regulating body temperature, metabolism, and heart rate.

Researchers indicated T₃ remained low during the recovery phase and suggested a longer time of increased caloric intake for the diet group. An increased recovery period would help reduce the risk of long-term hormone changes and imbalance.

Other Health Concerns and Information

Another study examined exercise dependence and muscle dysmorphia in female bodybuilders. Body image issues and dissatisfaction can become a problem in sports like bodybuilding. The drive for body perfection pushes some female and male lifters to develop an obsessive approach to bodybuilding that is psychologically damaging. It appears female competitive bodybuilders are more at risk to develop exercise dependence or muscle dysmorphia compared to women who lift recreationally.

  • Exercise dependence (ED): compulsive cravings for exercise leading to excessive exercise behaviors without regard to potential negative health consequences.
  • Muscle dysmorphia (MD): the opposite of anorexia nervosa and sometimes referred to as bigorexia. A bodybuilder with MD believes they are too thin or underdeveloped when they are actually quite large and muscular.

Other research indicated disordered eating can become a problem for athletes participating in lean build sports. Female bodybuilders and fitness competitors are at higher risk of introducing restrictive and disordered eating behaviors. This is partly due to improper or no nutritional guidance from experts. Working with a registered dietitian (RD) specializing in sports nutrition is advised to help athletes implement proper and safe training methods.

Another study indicated prolonged extreme dieting is often associated with unhealthy body fat levels, decreased muscle mass, and decreased bone density. It was suggested recovering from undernutrition could be slow and difficult.

Further studies are recommended to gain more conclusive information on the effects of diet and recovery on normal-weight active females. Since competitive fitness women typically enter multiple competitions, more research on repetitive extreme dieting and long-term negative health effects are needed.

Research Summary and Takeaway

Females preparing for fitness and bodybuilding competitions want to lose fat weight and maintain muscle. This research has indicated some positives and negatives to severe weight loss trying to accomplish these goals. The following bullet points are valuable takeaways:

  • Lean muscle was minimally decreased overall in most women dieting for competition.
  • A significant decrease in fat mass was achieved by all dieting participants.
  • Muscle function and strength was well preserved during the diet phase.
  • Hormone function was adversely affected by diet and severe weight/fat loss.
  • Leptin hormone levels returned to normal values in all women during the recovery phase.
  • Estradiol (estrogen) returned to normal levels in all women during the recovery phase.
  • Testosterone levels remained at below normal values even during the recovery phase. 
  • Women should continue a longer recovery phase with increased calories until T₃ hormone and testosterone return to normal levels.

A Word From Verywell

The sport of female bodybuilding and competitive fitness continues to grow in popularity. Many women are ready to take fitness to the next level and want to be well-informed on the subject. You may be ready to take this step but feel uneasy about the dieting process and possible health consequences.

The positive research findings show dieters can lose some fat and maintain muscle mass, but at a cost of hormonal imbalances with unknown long-term implications (and potentially a loss of muscle strength). As a female bodybuilder or fitness competitor, it will be important to stay up-to-date with the research. Before making the choice to start training for competitive fitness or bodybuilding, consulting with a registered sports nutrition specialist may also be beneficial.

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