Changes in muscle strength after diet-induced weight reduction in adult men with obesity: a prospective study

Figures & data

Figure 1 Flow chart of participant recruitment.

Abbreviation: BMI, body mass index.

Table 1 Total energy intake before and after a 12-week dietary restriction program

Parameter	Pre (range)	Post (range)	Change (95% CI)	P
Total energy intake, kcal/d	2,228.8 ± 570.6 (1,385.0, 3,546.0)	1,593.9 ± 198.3 (1,187.0, 2,013.0)	−634.9 ± 559.8 (−871.3, −398.5)	<0.01
Carbohydrate, g/d	279.5 ± 92.5 (133.6, 566.8)	204.4 ± 27.0 (144.9, 261.1)	−75.1 ± 88.9 (−112.6, −37.6)	<0.01
Protein, g/d	83.2 ± 17.9 (49.2, 119.0)	72.3 ± 14.6 (42.6, 103.1)	−10.9 ± 19.7 (−19.3, −2.6)	<0.05
Fat, g/d	68.6 ± 24.4 (24.8, 132.0)	47.2 ± 10.6 (28.8, 74.8)	−21.5 ± 27.7 (−33.2, −9.78)	<0.01

Note: Values represent the mean ± standard deviation (range).

Table 2 Characteristics of participants before and after a 12-week dietary modification program

Parameter	Pre (range)	Post (range)	Change (95% CI)	P
Age, year	52.4 ± 10.0 (32.0, 64.0)
Height, cm	168.8 ± 6.4 (156.1, 184.6)
Weight, kg	83.4 ± 11.0 (70.4, 102.7)	73.2 ± 14.3 (61.7, 97.2)	−8.8 ± 3.6 (−10.3, −7.2)	<0.01
Body mass index, kg/m^2	29.2 ± 2.6 (25.7, 34.7)	26.1 ± 2.6 (22.5, 32.7)	−3.1 ± 1.3 (−3.6, −2.5)	<0.01
% WF, kg	25.1 ± 4.0 (18.9, 33.4)	21.5 ± 4.9 (14.3, 32.4)	−3.7 ± 2.3 (−4.7, −2.7)	<0.01
Arm muscle mass, kg	6.6 ± 1.0 (5.1, 9.2)	6.4 ± 1.1 (4.7, 9.1)	−0.2 ± 0.5 (−0.4, 0.1)	0.10
Leg muscle mass, kg	19.6 ± 3.1 (15.9, 26.4)	18.4 ± 3.1 (14.3, 25.3)	−1.2 ± 0.7 (−1.5, −0.9)	<0.01
SMI, kg	9.2 ± 0.9 (7.8, 11.2)	8.7 ± 0.9 (7.0, 10.8)	−0.5 ± 0.3 (−0.6, −0.4)	<0.01
% MMI, %	31.5 ± 3.0 (25.3, 37.2)	33.5 ± 3.9 (26.9, 40.2)	2.0 ± 1.6 (1.3, 2.6)	<0.01
HGS	45.3 ± 6.1 (34.5, 56.6)	44.2 ± 5.8 (35.9, 57.6)	−1.0 ± 3.2 (−2.4, 0.3)	0.12
HGS/BW, kg	0.55 ± 0.08 (0.44, 0.73)	0.64 ± 0.22 (0.43, 0.77)	0.05 ± 0.05 (0.03, 0.07)	<0.01
IMT60 PTQ, Nm	214.1 ± 53.8 (136.2, 347.9)	192.6 ± 43.3 (116.0, 322.0)	−21.5 ± 30.4 (−34.3, −8.7)	<0.01
IMT60 PTQ/BW, Nm/kg	2.56 ± 0.51 (1.79, 3.52)	2.77 ± 1.07 (1.61, 3.58)	0.03 ± 0.36 (−0.12, 0.19)	0.36
IKT60 PTQ, Nm	177.8 ± 53.2 (101.3, 347.9)	161.1 ± 46.6 (73.8, 281.8)	−16.7 ± 14.9 (−23.0, −10.3)	<0.01
IKT60 PTQ/BW, Nm/kg	2.13 ± 0.50 (1.27. 3.43)	2.29 ± 0.88 (1.02, 3.14)	0.03 ± 0.19 (−0.04, 0.11)	0.36
IKT60 TW, J	496.5 ± 136.8 (272.1, 838.4)	462.1 ± 127.3 (213.6, 793.4)	−34.3 ± 35.8 (−49.5, −19.2)	<0.01
IKT60 AP, W	110.8 ± 34.8 (62.0, 209.1)	102.4 ± 30.8 (47.0, 188.3)	−8.4 ± 8.7 (−12.0, −4.7)	<0.01

Note: Values represent the mean ± standard deviation (range).

Abbreviations: HGS, handgrip strength; HGS/BW, handgrip strength/body weight; IKT60 AP, isokinetic 60 average power; IKT60 PTQ, isokinetic 60 peak torque; IKT60 PTQ/BW, isokinetic 60 peak torque/body weight; IMT60 PTQ, Isometric60 peak torque; IMT60 PTQ/BW, isometric 60 peak torque/body weight; IKT60 TW, isokinetic 60 total work; % MMI, percentage of muscle mass index; SMI, skeletal muscle mass index; % WF, percentage of whole-body fat mass.

Table 3 Partial correlation coefficients adjusted for agea

	Weight	Leg muscle mass	IMT60 PTQ, Nm	IMT60 PTQ/BW, Nm/kg	IKT60 PTQ, Nm	IKT60 PTQ/BW, Nm/kg	IKT60 TW, J	IKT60 AP, W
Weight, kg		0.47*	0.07	−0.75**	0.11	−0.72**	0.09	0.12
Leg muscle mass, kg	0.63**		0.63**	0.07	0.64**	0.08	0.67**	0.61**
IMT60 PTQ, Nm	0.33	0.70*		0.47*	0.86**	0.43*	0.86**	0.87**
IMT60 PTQ/BW, Nm/kg	−0.29	0.29	0.80**		0.42*	0.97**	0.42*	0.40
IKT60 PTQ, Nm	0.23	0.58**	0.80**	0.64**		0.60*	0.97**	0.98**
IKT60 PTQ/BW, Nm/kg	−0.33	0.20	0.61**	0.82**	0.83**		0.49*	0.47*
IKT60 TW, J	0.22	0.68**	0.82**	0.68**	0.92**	0.77**		0.97**
IKT60 AP, W	0.23	0.62**	0.80**	0.67**	0.96**	0.81**	0.95**

Notes:

a Values in the lower left half of the table represent correlations between variables before the weight loss program; values in the right half (boldface) of the table represent correlations between changes in variables after the weight loss program.

* P < 0.05.

** P < 0.01.

Abbreviations: IKT60 AP, isokinetic 60 average power; IKT60 PTQ, isokinetic 60 peak torque; IKT60 PTQ/BW, isokinetic 60 peak torque/body weight; IKT60 TW, isokinetic 60 total work; IMT60 PTQ, isometric 60 peak torque; IMT60 PTQ/BW, isometric 60 peak torque/body weight.

Table 4 Correlations between the rates of change in lower extremity muscle mass and body weight and lower extremity muscle strength adjusted for age

Rates of change in lower extremity muscle mass
	Rate of change in body weight	Rate of change in IMT60 PTQ	Rate of change in IKT60 PTQ	Rate of change in IKT60 TW	Rate of change in IKT60 AP
			−6.0 ± 3.6%
	−10.5 ± 4.1%	−8.7 ± 12.5%	−9.3 ± 7.6%	−6.8 ± 7.7%	−7.2 ± 8.2%
R ^2	0.03	0.03	0.06	0.11	0.01
P	0.41	0.46	0.25	0.12	0.84

Note: Values represent the mean ± standard deviation.

Abbreviations: IMT60 PTQ, isometric 60 peak torque; IKT60 PTQ, isokinetic 60 peak torque; IKT60 TW, isokinetic 60 total work; IKT60 AP, isokinetic 60 average power.