Successful Dieting [4/5]: How Much Carbohydrate? (with or without exercise)

A practical carbohydrate threshold appears to exist where further reductions negatively impact performance and put one at risk for LBM losses. Find out how much carbs you need in a diet.

Longland et al. (1)

Previously I examined this study in the context of protein intake. Now it is time to look at the carbohydrate content and relate it with other studies, such as Pasiakos et al (2013) I also covered before.

To recapitulate, this study experimented with different amounts of protein and exercise during an energy deficit of 40% for 4 weeks. Subjects were overweight but not obese and were randomly assigned (n = 20/group) to consume either a lower-protein (1.2 g/kg) control diet (CON) or a higher-protein (2.4 g/kg) diet (PRO). Participants were provided with all meals and beverages to consume throughout the intervention period. The control group consumed 15% protein, 50% carbohydrates, and 35% fat vs. 35% protein, 50% carbohydrates, and 15% fat in the PRO group. Both groups consumed the same carbohydrate content at 50%.

After 4 weeks LBM increased in the PRO group (1.2 kg) and to a greater extent compared with the CON group (0.1 kg). The PRO group had a greater loss of fat mass than did the CON group (-4.8kg vs. -3.5 kg). Note that even the control group with 1.2g/kg of protein was able to maintain LBM.

Mettler et al. (2)

In this study, 20 young healthy resistance-trained athletes were examined for energy expenditure for 1 week and fed a mixed diet (15% protein, 100% energy). During week 2, all subjects were provided with food containing 100% of their habitual energy with a macronutrient composition of 50% carbohydrate, 15% protein, and 35% fat.

In weeks 3 and 4 they followed a hypoenergetic diet (60%) and were allocated either to the control group (50.2% carbohydrate, 15% protein (1g/kg), 34.8% fat) or to the high-protein group (50.8% carbohydrate, 35% protein (2.31g/kg), and 15% fat).

Total (3.0 ± 0.4 and 1.5 ± 0.3 kg for the CP and HP, respectively) and lean body mass loss (1.6 ± 0.3 and 0.3 ± 0.3 kg) were significantly larger in the CP compared with those in the HP.

Garthe et al. (3)

The aim of this study was to compare changes in body composition, strength, and power during a weekly body-weight (BW) loss of 0.7% slow reduction (SR) vs. 1.4% fast reduction (FR). Twenty-four athletes followed energy-restricted diets promoting the predetermined weekly WL. They consumed about 1.2–1.8 g/kg of daily protein, 3.2–3.6 g/kg of daily carbohydrate (54-55.5%) and 20% of fat.

BW and fat mass decreased in both SR and FR by 5.6% ± 0.8% and 5.5% ± 0.7% (0.7% ± 0.8% vs. 1.4% ± 0.4%/wk) and 31% ± 3% and 21 ± 4%, respectively. LBM increased in SR by 2.1% whereas it was unchanged in FR.

Pasiakos et al (4).

This study found that lean mass retention tended to be greater in a group consuming 1.6 g/kg/day versus a group consuming 2.4 g/kg/day (7). In this study subjects received protein diets of 0.8g/kg (RDA), 1.6 g/kg (2x RDA) and 2.4 g/kg (3x RDA) for periods of 21 days with 40% of energy deficit.

Dietary fat accounted for no more than 30% of total energy, and carbohydrate provided the remainder of the prescribed energy.

After simple math, carbohydrate percentages were 57%, 44% and 27% for RDA, 2xRDA and 3xRDA groups, respectively.

Overall, volunteers lost 3.2 kg during the 21-d ED; 3.5 kg for RDA, 2.7 kg for 2xRDA, and 3.3 kg for 3xRDA. The 2x RDA group lost more fat mass (70.1%) followed by the 3x RDA (63.6%), and then RDA (41.8%). Lean body mass loss was lower for the 2x RDA (29.9%) followed by the 3x RDA (36.4%) compared to RDA (58.2%). Results indicated then that the 2x RDA with 1.6g/kg lost more body fat and the less lean body mass and was better in both regards than 3x RDA.

Kistler et al. (5)

In this case study, the athlete undertook a calorically restrictive diet for a 26-week preparation to a bodybuilding contest. At the start of contest preparation, the bodybuilder consumed 250 g protein, 240 g carbohydrate, and 70 g fat per day on 5 days of the week (2590kcal 37% carbs). On 2 high-carbohydrate days evenly spaced throughout the week, 225 g protein, 400 g carbohydrate, and 65 g fat was consumed daily.

When rate of weight loss slowed, a 5 to 10g reduction in daily fat or carbohydrate intake was implemented to maintain weight loss. At the end of contest preparation, the bodybuilder was consuming 250 g protein, 140 g carbohydrate, and 51 g fat per day on 5 days of the week (2019kcal 27% carbs) and 225 g protein, 255 g carbohydrate, and 46 g fat per day on two days of the week.

Since carbohydrate intake was variable I will use a value of 32% for the table at the end. Body weight dropped from 91.1 to 71.1 (-20kg) and percent body fat dropped from 17.5 to 7.4% (-10.4kg) during preparation. There was also a reduction in lean mass (–8.8%, 6.6kg).

Note also that bone mineral content/density increased.

Rossow et al (6).

This case study tracked a drug-free male bodybuilder (age 26–27 y) for the 6 months before and after a competition.

Initially during the preparation period, the subject’s daily macronutrient breakdown was 36% protein (PRO), 36% carbohydrate (CHO), and 28% fat for 5 days per week and 30% PRO, 48% CHO, and 22% fat for 2 days of the week. During the preparation period, overall caloric intake did not change dramatically, but modest (5–10 g) weekly reductions in CHO and/or fat were made based on the progression of weight loss. Just before competition, the daily macronutrient breakdown was 46% PRO, 29% CHO, and 25% fat.

Percent body fat declined from 14.8% to 4.5% during preparation and returned to 14.6% during recovery. Strength decreased during preparation and did not fully recover during 6 months of recovery. Testosterone declined from 9.22 to 2.27 ng/mL during preparation and returned back to the baseline level, 9.91 ng/mL, after competition. During competition preparation, fat-free mass did not decrease greatly (–3.9%, 2.81kg).

Robinson et al. (7)

This case study documents a structured nutrition and conditioning intervention followed by a 21 year-old amateur bodybuilding competitor to improve body composition. Absolute (relative) carbohydrate, fat, and protein intake over the 14 weeks was 100 ± 56 g/d (20 ± 3% energy), 79 ± 17 g/d (37 ± 4% energy) and 212 ± 13 g/d (45 ± 8% energy), respectively.

This strategy resulted in a body mass loss of 11.7 kgs, corresponding to a 6.7 kg reduction in fat mass and a 5.0 kg reduction in fat-free mass. This equated to an average weight loss of 0.98%/week. The energy deficit was 882 ± 433 kcal/d.

It looks from the table that there is a lower threshold for carbohydrate intake bellow which more lean body mass is lost, in other words carbohydrate intake below a certain threshold ceases to be protective of lean body mass. All studies and groups (except RDA in Pasiakos et al) had higher/high protein, and the weight loss rate per week was around the same at 0.5-1.0 % BW (1.4% BW/week in the higher protein group for Longland et al.).

It looks like when carbohydrate intake drops below 32% it ceases to be protective of lean body mass. I would say, keeping carbohydrate intake above 32-35%, or more precisely perhaps above 2g/kg is advisable to spare lean body mass as much as possible.

(Robinson et al. had some issues with the training program that probably also contributed to the greater loss of lean body mass).

Would you like to know more?


1. Thomas M Longland, Sara Y Oikawa, Cameron J Mitchell, Michaela C Devries, and Stuart M Phillips. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr 2016;103:738–46.
2. Mettler S, Mitchell N, Tipton KD (2010). Increased protein intake reduces lean body mass loss during weight loss in athletes. Med Sci Sports Exerc 42(2):326–337
3. Ina Garthe, Truls Raastad, Per Egil Refsnes, Anu Koivisto, and Jorunn Sundgot-Borgen. Effect of Two Different Weight-Loss Rates on Body Composition and Strength and Power-Related Performance in Elite Athletes. International Journal of Sport Nutrition and Exercise Metabolism, 2011, 97-104
4. Pasiakos SM, Cao JJ, Margolis LM, et al. Effects of high-protein diets on fat-free mass and muscle protein synthesis following weight loss: a randomized controlled trial. FASEB J. 2013;27:3837–47.
5. Brandon M. Kistler, Peter J. Fitschen, Sushant M. Ranadive, Bo Fernhall, and Kenneth R. Wilund. Case Study: Natural Bodybuilding Contest Preparation. International Journal of Sport Nutrition and Exercise Metabolism, 2014, 24, 694 -700
6. Lindy M. Rossow, David H. Fukuda, Christopher A. Fahs, Jeremy P. Loenneke, and Jeffrey R. Stout. Natural Bodybuilding Competition Preparation and Recovery: A 12-Month Case Study. International Journal of Sports Physiology and Performance, 2013, 8, 582-592
7. Scott Lloyd Robinson1, Anneliese Lambeth-Mansell, Gavin Gillibrand, Abbie Smith-Ryan and Laurent Bannock. A nutrition and conditioning intervention for natural bodybuilding contest preparation: case study. Journal of the International Society of Sports Nutrition (2015) 12:20